National Nurses United Covid-19 Bibliography

1. Yanes-Lane et al., “Proportion of asymptomatic infection among COVID-19 positive persons and their transmission potential: A systematic review and meta-analysis,” PLOS ONE, November 2020, link.

Summary:

• This study conducted a systematic review and meta-analysis on the proportion of asymptomatic infection among Covid-19 positive individuals and their transmission potential.
• Researchers found that the proportion of asymptomatic Covid-19 infections at time of testing ranged from 20 to 75%. Meta-analysis estimated a secondary attack rate of 18.8% in contacts of asymptomatic cases.

2. Abkarian et al., “Speech can produce jet-like transport relevant to asymptomatic spreading of virus,” Proceedings of the National Academy of Sciences, September 2020, link.

Summary:

• This study examined and visualized airflows during breathing and speaking, with a high-speed camera to capture the movement of aerosols.
• Researchers found that normal conversations can create a turbulent, jet-like airflow that can transport exhaled breath over 2 meters (6.5 feet) in front of the speaker, potentially further, within 30 seconds. The results of this study are relevant to asymptomatic spread of SARS-CoV-2 as transmission can occur in the absence of a cough. It also highlights the importance of the proximity to, and time spent with an asymptomatic speaker, especially in indoor settings.

3. Buitrago-Garcia et al, “Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: A living systematic review and meta-analysis,” PLOS Medicine, September 2020, link.

Summary:

• Literature review and meta-analysis of papers on asymptomatic/presymptomatic transmission published through June 10.
• 20% of people with SARS-CoV-2 infections remain asymptomatic during follow-up “but biases in study designs limit the certainty of this estimate.”

4. Sugano et al., “Cluster of SARS-CoV-2 infections linked to music clubs in Osaka, Japan: asymptomatically infected persons can transmit the virus as soon as 2 days after infection,” J of Infectious Diseases, August 2020, link.

Summary:

• Report on a case cluster linked to music clubs in Japan with 108 cases.
• The index case was a health care worker who was exposed at work on Feb 14 and attended a club on Feb 15 and developed symptoms on Feb 24.
• The index case transmitted the virus while symptomatic. Within the cluster, all cases transmitted the virus within 2 to 3 days of exposure.

5. Corcorran et al., “Prolonged persistence of PCR-detectable virus during an outbreak of SARS-CoV-2 in an inpatient geriatric psychiatry unit in King County, Washington,” American Journal of Infection Control, August 2020, link.

Summary:

• This study described key characteristics, interventions, and outcomes of a SARS-CoV-2 outbreak within an inpatient geriatric psychiatry unit at the University of Washington Medical Center – Northwest.
• Researchers identified 10 patients and 7 staff members with SARS-CoV-2 infection; 30% of patients remained asymptomatic over the course of infection. The median duration of PCR positivity was 25.5 days among symptomatic patients and 22.0 days among asymptomatic patients. Cycle threshold values (viral load) was similar between symptomatic and asymptomatic patients.

6. Lee et al., “Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea,” JAMA Internal Medicine, August 2020, link.

Summary:

• Cohort study of patients from South Korea (n=303), including 110 who were asymptomatic at time of isolation (19.1% went on to develop symptoms during isolation).
• Upper and lower respiratory tract samples were taken, and viral load was measured.
• Asymptomatic patients had very similar viral loads to symptomatic patients.

7. Long et al., “Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections,” Nature Medicine, June 2020, link.

Summary:

• Researchers compared Covid-19 antibody responses of 37 asymptomatic patients and 37 symptomatic patients in China. They found that asymptomatic group had a significantly longer duration of viral shedding than the symptomatic group. In addition, IgG levels and neutralizing antibodies diminished significantly within 2 to 3 months after infection. No antibodies were detected 8 weeks after recovery in 40% of asymptomatic group and 12.9% of symptomatic group.

8. Widders et al., “SARS-CoV-2: The viral shedding vs infectivity dilemma," Infection, Disease & Health, May 2020, link.

Summary:

• This study evaluated the evidence around viral shedding and infectivity of SARS-CoV-2.
• Researchers found that the percentage of asymptomatic SARS-CoV-2 infections range from 1% to 78%. They also found that immunosuppression and disease severity appear to prolong the duration of viral shedding; though, the correlation between duration of shedding and infectivity is unclear.

9. Kimball et al., “Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020,” Morbidity and Mortality Weekly Report (MMWR) 2020;69:377–381, link.

Summary:

• This study examined infections in a long-term care skilled nursing facility in Washington.
• Researchers found that 56.5% of residents were infected and infectious but asymptomatic at the time of testing. They also note that symptom-based screening of nursing home residents might fail to identify all SARS-CoV-2 infections.

1. Zhou et al., “Breath-, air- and surface-borne SARS-CoV-2 in hospitals,” Journal of Aerosol Science, October 2020, link.

Summary:

• Exhaled breath condensate (EBC) samples were collected from 13 recruited patients. Nine were recovering Covid-19 patients and four had influenza symptoms and repeatedly tested negative for SARS-CoV-2 using throat swabs.
• 318 swab samples were collected from surfaces associated with the Covid-19 patients and medical staff, and from many other surfaces inside four hospitals in Wuhan.
• 44 air samples were collected from the corridors, hospital waste storage rooms, ICU rooms, toilets, medical preparation rooms, clinical observation rooms, and general wards.
• Researchers detected SARS-CoV-2 in exhaled breath (22.2%), air samples (6.8%), and surface swabs (3.1%) collected from hospitals of Wuhan using both RT-PCR and digital PCR. Two recovering Covid-19 patients, in Wuhan hospitals, ready for hospital discharge were emitting SARS-CoV-2 RNA, about (7.35–7.77) x 104 viruses per hour estimated by the method described, via breathing.
• RT-PCR diagnosis using throat swab specimens had a failure rate of more than 22% in safely discharging Covid-19 patients who were otherwise still exhaling the SARS-CoV-2 by a rate of estimated ~1400 RNA copies per minute into the air.
• Direct surface contact might not represent a major transmission route, and lower positive rate of air sample (6.8%) was likely due to natural ventilation (1.6–3.3 m/s) and regular disinfection practices.

2. Riddell et al., “The effect of temperature on persistence of SARS-CoV-2 on common surfaces,” Virology Journal, October 2020, link.

Summary:

• This study measured the survival rates of infectious SARS-CoV-2 virus, suspended in a standard ASTM E2197 matrix, on several common surface types. All experiments were carried out in the dark, to negate any effects of UV light.
• Inoculated surfaces were incubated at 20 °C (68 °F ~room temp), 30 °C and 40 °C and sampled at various time points.
• The study found that viable virus was isolated for up to 28 days at 20 °C from common surfaces such as glass, mobile phones, stainless steel and both paper and polymer banknotes. Conversely, infectious virus survived less than 24 hours at 40 °C on some surfaces.
  • SARS-CoV-2 survived longer at lower temperatures; lasted longer on smooth surfaces than porous surfaces such as cotton.
  • SARS-CoV-2 lasted 10 days longer than influenza on some surfaces
• While the primary spread of SARS-CoV-2 appears to be via aerosols and respiratory droplets, fomites may also be an important contributor in transmission of the virus.

3. Miller et al., “Transmission of SARS‐CoV‐2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event,” Indoor Air, September 2020, link.

Summary:

• Detailed investigation of the Skagit County choir outbreak from WA early in outbreak.
• 1 index case led to 53 cases identified from 61 individuals in attendance (33 confirmed via testing, 20 probable based on timing and symptoms).
• No spatial pattern was identified in the distribution of cases. The heater was on (with MERV11 filter and unknown outdoor air proportion) at beginning of rehearsal but probably turned off with so many people in the room because it was 45 deg F outside.
• The index case did not participate in moving chairs or handling snacks so fomite transmission unlikely. No common points of contact were identified (e.g., bathroom handle only common for about 6 other people).
• No one was located within 3 m in front of the index case; therefore, droplet transmission did not occur. The paper goes through other details to very clearly rule out droplet transmission. This virus was transmitted via aerosols/airborne.

4. Lednicky et al., “Viable SARS-CoV-2 in the air of a hospital room with Covid-19 patients,” International Journal of Infectious Diseases, September 2020, link.

Summary:

• Researchers recovered viable (infectious) SARS-CoV-2 virus in the air from a hospital room with 1 Covid-19 patient and a 2nd patient who had previously tested positive for Covid-19 but tested negative prior to the study. The air was collected 2 to 4.8 meters (6.5 to 15.7 feet) away from the patients.
• Airborne virus was detected in the absence of health-care aerosol-generating procedures.
• The virus strain detected in the aerosols matched the virus strain isolated from a patient with acute Covid-19.

5. de Man et al., “Outbreak of Coronavirus Disease 2019 (COVID-19) in a Nursing Home Associated with Aerosol Transmission as a Result of Inadequate Ventilation,” Clinical Infectious Diseases, August 2020, link.

Summary:

• Paper reports on the investigation of a Covid-19 outbreak in a Dutch nursing home where 81% of residents and 50% of health care workers in 1 ward were diagnosed with Covid-19 but tests of all residents and workers in 6 other wards were negative.
• Direct transmission cannot be ruled out, but the rate of transmission was extremely rapid. Investigators found that the outbreak ward’s ventilation system had been recently renovated and a CO2 controlled energy-efficient system was installed.
• That meant that indoor air was only refreshed when the CO2 level exceeded 1000 ppm. Otherwise, indoor air was recirculated.
• The other 6 wards (with no infections) were ventilated with outdoor air, indicating that aerosol transmission via the ventilation system was likely at play in the outbreak

6. Tang et al., “Aerosol transmission of SARS-CoV-2? Evidence, prevention and control,” Environment International, August 2020, link.

Summary:

• Literature review reporting on the overwhelming evidence for aerosol transmission. Notes the need for airborne precautions for health care workers.

7. Ma et al., “Covid-19 patients in earlier stages exhaled millions of SARS-CoV-2 per hour,” Clinical Infectious Diseases, August 2020, link.

Summary:

• Researchers collected exhaled breath condensate from 57 Covid-19 patients, 4 hospitalized non-Covid-19 patients, and 15 healthy individuals in Beijing. Exhaled breath samples had the highest positive rate (26.9%); Covid-19 patients emitted millions of SARS-CoV-2 particles into the air per hour.
• Air samples and surface swabs were also collected from quarantine hotels and hospitals. Toilet room air and surface swab samples were most likely to be positive, followed by hospital floor, other surfaces, patient touching surfaces, and medical touching surfaces.

8. Monroe et al., “Incidence and Persistence of Viral Shedding in Covid-19 Post-acute Patients with Negativized Pharyngeal Swab: A Systematic Review,” Frontiers in Medicine, August 2020, link.

Summary:

• Literature review examining 147 studies measuring viral shedding in patients.
• Researchers found variation in length of time patients shed SARS-CoV-2 virus in different body fluids. The fecal viral positivity duration was (median 19 days) longer than respiratory tract viral positivity (median 14 days).

9. Santarpia et al., “Aerosol and surface contamination of SARS-CoV-2 observed in quarantine and isolation care,” Scientific Reports, July 2020, link.

Summary:

• Researchers collected air and surface samples to examine viral shedding from isolated Covid-19 patients. Significant environmental contamination was found in bedrails, toilets, ventilation grates, window ledges and hallways.  
• SARS-CoV-2 was found in air samples taken greater than 6 feet from the patients.
• SARS-CoV-2 was found in air samples worn by sampling personnel, even in the absence of cough.  

10. Santarpia et al., “The Infectious Nature of Patient-Generated SARS-CoV-2 Aerosol,”medRxiv, July 2020, link.

Summary:

• This study looked at the presence and viral replication of SARS-CoV-2 in aerosol samples around 6 patients admitted into mixed acuity wards in April 2020. Samples were collected greater than 6 feet from patients, beyond the foot of the bed.
• SARS-CoV-2 RNA was found in respired aerosols <5 µm around all 6 patients. When placed in cell cultures, aerosol samples <1 µm in diameter replicated.
• Researchers note that the study shows that some aerosol particles smaller than 5µm produced through normal breathing, vocalization, and coughing can contain infectious SARS-CoV-2.

11. Fears et al., “Persistence of Severe Acute Respiratory Syndrome Coronavirus 2 in Aerosol Suspensions,” Emerging Infectious Diseases, June 2020, link.

Summary:

• This study looked at the viability of SARS-CoV-2 in suspended aerosols and found that SARS-CoV-2 remained infectious after 16 hours suspended in aerosols. This further reinforces airborne/aerosol transmission of SARS-2.
• The authors state: “Our approach of quantitative measurement of infectivity of viral airborne efficiency complemented by qualitative assessment of virion morphology leads us to conclude that SARS-CoV-2 is viable as an airborne pathogen.”

12. Kasloff, Samantha B. et al., “Stability of SARS-CoV-2 on Critical Personal Protective Equipment,” medRxiv, June 2020, link.

Summary:

• Studied how long SARS-CoV-2 virus can survive on different surfaces in the healthcare environment, including nitrile medical examination gloves, reinforced chemical resistant gloves, N-95 and N-100 particulate respirator masks, Tyvek coveralls, plastic from face shields, heavy cotton, and stainless steel.
• Coupons of each type of material were inoculated with SARS-CoV-2 virus along with compounds meant to mimic the organic components of virus-containing fluid typically shed by patients. Coupons were then dried and maintained at ambient temperature and humidity (35-40%).
• The study found viable virus on the following surfaces for the following time frames (max time studied was 21 days):
  • Plastic (from face shield) up to 21 days
  • N-95 respirator up to 21 days, with significant quantity of virus recovered after 14 days
  • N-100 respirator up to 21 days
  • Tyvek up to 14 days
  • Stainless steel up to 14 days
  • Nitrile gloves up to 7 days
  • Chemical resistant gloves up to 4 days
  • Cotton up to 24 hours
• This study starkly underlines the risks of reusing single-use N-95 respirators and other single-use PPE. And it underlines the importance of effective cleaning protocols for powered air-purifying respirators (PAPRs), elastomeric respirators, and other PPE designed for reuse.

13. Chia, Po Ying et al., “Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients,” Nature Communications, May 2020, link.

Summary:

• This study examined surface and air contamination in airborne infection isolation rooms of patients with confirmed Covid-19 infections in Singapore.
• They found that 56.7% of the rooms had at least one environmental surface contaminated, with 18.5% of the toilet seats and toilet flush button being contaminated.
• High touch surface contamination was shown in ten (66.7%) out of 15 patients in the first week of illness, and three (20%) beyond the first week of illness (p = 0.010).
• Air sampling of two Covid-19 patients (both day 5 of symptoms) detected SARS-CoV-2 PCR positive particles of sizes >4 µm and 1-4 µm. In a single subject at day 9 of symptoms, no SARS-CoV-2 PCR-positive particles were detected.

14. van Doremalen et al., “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1,” New England Journal of Medicine, April 2020, link.

Summary:

• This study examined how long SARS-CoV-2 can survive in aerosols suspended in the air and on surfaces of different types (metal, plastic, cardboard).
• They found that SARS-CoV-2 can survive up to three hours in aerosols, four hours on copper, 24 hours on cardboard, 2-3 days on plastic and stainless steel.
• The authors conclude, “Our results indicate that aerosol and fomite transmission of [SARS-CoV-2] is plausible, as the virus can remain viable in aerosols for multiple hours and on surfaces up to days.” This study was conducted by NIH and CDC scientists in addition to UCLA and Princeton.

15. Leung, Nancy H. L. et al. “Respiratory virus shedding in exhaled breath and efficacy of face masks,” Nature Medicine, April 2020, link.

Summary:

• This study examined viral presence and load in exhaled breath of patients with lab-confirmed influenza, seasonal coronaviruses, or rhinovirus.
• Found viral presence in exhaled breath, even without cough, for all types of viruses in both droplet (>5 micron) and aerosol (<5 micron) particles.

16. Chin, Alex W H et al., “Stability of SARS-CoV-2 in different environmental conditions,” The Lancet Microbe, April 2020, link.

Summary:

• This study examined the ability of SARS-CoV-2 to survive outside the human body in different environmental conditions.
• They found that SARS-CoV-2 can survive outside the human body for up to 14 days at 39 degrees Fahrenheit, 7 days at 72 degrees Fahrenheit and remains infectious in both situations.
• They found that SARS-CoV-2 can survive on different surfaces:
  • Printing and tissue papers- up to 3 hours
  • Wood and cloth- up to 2 days
  • Glass and banknote- up to 4 days
  • Stainless steel and plastic- up to 7 days
  • Surgical mask- detectable level of infectious virus found after 7 days on outer layer of mask
• They also tested the impact of different disinfectants, used at working concentrations, to successfully inactivate SARS-CoV-2:
  • Household bleach (1:49)
  • Household bleach (1:99)
  • Ethanol (70%)
  • Povidone-iodine (7.5%)
  • Chloroxylenol (0.05%)
  • Chlorhexidine (0.05%)
  • Benzalkonium chloride (0.1%)

17. Wölfel, Roman, et al., “Virological assessment of hospitalized patients with Covid-2019,” Nature, April 2020, link.

Summary:

• This study examined viral loads and isolates for patients hospitalized with Covid-19. The majority of patients in this study presented with upper respiratory tract symptoms. Viral loads from upper respiratory tract samples were extremely high (more than 1000 times higher than SARS). Live virus was isolated from upper respiratory tract tissues.
• Michael Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said, “The findings [of this study] confirm that Covid-19 is spread simply through breathing, even without coughing… They also challenge the idea that contact with contaminated surfaces is a primary means of spread,” (emphasis added). http://www.cidrap.umn.edu/news-perspective/2020/03/study-highlights-ease-spread-covid-19-viruses.

18. Guo, Zhen-Dong et al., “Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020,” Emerging Infectious Diseases, April 2020, link.

Summary:

• This study looked at environmental contamination in an ICU and a general ward in hospital in China where patients with Covid-19 were placed.
• They found SARS-CoV-2 on many surfaces in patient rooms and on units, including doorknobs, bedrails, patient masks, computer mouse, keyboards, etc.
• Many positive results on floors not just in patient room but throughout the unit. 50% of the samples from the soles of healthcare workers’ shoes were positive.
• They also measured SARS-CoV-2 in air samples and found several air samples positive in addition to finding that the samples from the air outlets were positive for virus.
• Underlines nurses’ need for PPE!

19. Chin, Alex W H et al. “Stability of SARS-CoV-2 in different environmental conditions,” The Lancet Microbe, April 2020, link.

Summary:

• This study examined the ability of SARS-CoV-2 to survive outside the human body in different environmental conditions.
• They found that SARS-CoV-2 can survive outside the human body for up to 14 days at 39 degrees Fahrenheit, 7 days at 72 degrees Fahrenheit and remains infectious in both situations.
• They found that SARS-CoV-2 can survive on different surfaces:
  • Printing and tissue papers- up to 3 hours
  • Wood and cloth- up to 2 days
  • Glass and banknote- up to 4 days
  • Stainless steel and plastic- up to 7 days
  • Surgical mask- detectable level of infectious virus found after 7 days on outer layer of mask
• They also tested the impact of different disinfectants, used at working concentrations, to successfully inactivate SARS-CoV-2:
  • Household bleach (1:49)
  • Household bleach (1:99)
  • Ethanol (70%)
  • Povidone-iodine (7.5%)
  • Chloroxylenol (0.05%)
  • Chlorhexidine (0.05%)
  • Benzalkonium chloride (0.1%)

20. Bourouiba, Lydia, “Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of Covid-19,” JAMA, March 2020, link.

Summary:

• This paper reported on what is known about disease transmission via respiratory droplets created by human exhalations, sneezes, and coughs.
• Droplet transmission was originally defined in 1897, large and small droplets defined in 1930s. This model of infectious disease transmission hasn’t been updated since. And yet, the CDC and WHO maintain use of this paradigm despite more recent research.
• More recent research over the past few decades performed with instrumentation that better measures particle sizes and movement has determined that human exhalations, coughs, and sneezes (the things that supposedly create large droplets under old model) are actually made of multiphase turbulent gas clouds (a puff) that entrains ambient air and traps and carries clusters of particles of a wide range of sizes.
• This includes viral particles in people who are sick.
• Pathogen-carrying gas clouds emitted when people breath, cough, and sneeze can travel up to 23-27 feet.

Covid-19 infections can occur with exposures less than 15 minutes and/or beyond 6 feet in distance.

1. Karan et al., “The Risk of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmission from Patients with Undiagnosed Coronavirus Disease 2019 (COVID-19) to Roommates in a Large Academic Medical Center,” Clinical Infectious Diseases, June 2021, link.

Summary:

• This study analyzed all adult patients hospitalized at Brigham and Women’s Hospital in Massachusetts, between 1 September 2020 and 15 April 2021, to assess SARS-CoV-2 transmission between patients in shared rooms. During the study period, all patients were tested for SARS-CoV-2 via PCR on admission; symptomatic patients were tested twice 12 hours apart and isolated in single rooms until the second test returned negative; asymptomatic patients were tested once and managed with standard precautions while the test was pending.
• Index patients and exposed roommates were defined as follows:
  • Roommates were considered exposed if they shared a room for ≥15 minutes with an index patient during their infectious window, defined as 48 hours prior to symptom onset (or positive test in the absence of symptoms) until isolation.
  • Exposed roommates were tested if they remained hospitalized; discharged patients were contacted by phone whenever possible and offered testing.
  • Roommates who were not tested between 3 and 14 days following exposure were excluded from the study.
  • PCR-positive patients were excluded on the basis of serial high cycle thresholds and/or prior history of SARS-CoV-2 infection.
• A total of 11,290 patients were admitted to shared rooms, of whom 25 tested positive (median 3 days after admission, range 0–21 days). Almost 40% of patients that shared a hospital room with someone with occult SARS-CoV-2 infection became infected. The risk was highest for patients sharing rooms with individuals with very low Ct counts.
  • Median time-to-positivity was 5 days post-exposure (range 2–10); 33% initially tested negative before testing positive.
  • Only 1 index case and 2 roommates had been fully vaccinated at the time of exposure; one vaccinated roommate was infected by an unvaccinated index case.
  • The median interval from hospital admission until positive test among infected roommates was 9.5 days (IQR 7.8–12).
  • Ten exposed roommates tested positive after discharge (median 4.5 days post-discharge, IQR 2–7.75).
  • Patients were >6 feet apart with closed curtains in between; only 3 out of 12 infected roommates were exposed to aerosol-generating procedures.
• The authors noted, “Our study underscores the importance of isolating and testing all patients exposed to roommates with SARS-CoV-2, including those who have been discharged. The majority of exposed roommates tested positive after discharge, hence in the absence of active follow-up of exposed patients many nosocomial transmission events will be missed.”

2. de Oliveira et al., “Evolution of spray and aerosol from respiratory releases: theoretical estimates for insight on viral transmission,” Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, January 2021, link.

Summary:

• This paper provides a description of and exploration into the physics of aerosol and droplet emission, evaporation, and settling. It considers the important dynamics of composition (respiratory droplets are not just pure water but contain proteins and salts that impact evaporation rates) in the context of relative humidity and gravity-induced settling.
• They found that “The time-of-flight to reach 2m (6.5 feet) is only a few seconds resulting in a viral dose above the minimum required for infection, implying that physical distancing in the absence of ventilation is not sufficient to provide safety for long exposure times.”

3. Mack et al., “Implementation and Evolution of Mitigation Measures, Testing, and Contact Tracing in the National Football League, August 9–November 21, 2020,” MMWR, January 2021, link.

Summary:

• “Subsequent contact tracing identified multiple instances of transmission that likely occurred during <15 minutes of cumulative interaction within 1.8 meters (6 feet).” Some instances of transmission occurred with interactions less than 5 minutes.
• These findings led the National Football League to change their definition of “high risk contact” to go beyond the CDC’s definition of 15 minutes within 6 feet.

4. Kwon et al., “Evidence of Long-Distance Droplet Transmission of SARS-CoV-2 by Direct Air Flow in a Restaurant in Korea,” Journal of Korean Medical Science, November 2020, link.

Summary:

• This study investigated a restaurant outbreak in South Korea, where the index case infected two other people after 5 minutes of exposure from a distance of 6.5 meters (21 feet) and 4.8 meters (15 feet).
• Researchers collected data from credit card records, closed-circuit television (CCTV) footage, cell phone location data as well as interviews. Nasopharyngeal specimens of cases and close contacts were also collected and tested using RT-PCR. The authors concluded that transmission can occur at a distance greater than 6 feet if there is direct air flow from an infected person.

5. Pringle et al., “Covid-19 in a Correctional Facility Employee Following Multiple Brief Exposures to Persons with Covid-19 – Vermont, July–August 2020,” MMWR Early Release, October 2020, link.

Summary:

• Correctional officer contracted SARS-CoV-2 after multiple brief encounters with six asymptomatic incarcerated individuals. Each interaction lasted about 1 minute, totaling 17 minutes of exposure over an 8-hour shift.
• Infected inmates did not wear masks for some of the interactions, while the officer wore a microfiber cloth mask, gown, goggles and gloves, and maintained 6 feet the entire time.
• The correctional officer had no known contact with anyone else with Covid-19 and coronavirus cases were low in his home county and in the rest of the correctional facility at the time, leading researchers to conclude that his exposure most likely came from the brief encounters.

People infected with Covid-19 can remain infectious beyond 10 days after symptom onset.

6. Truong et al., “Persistent SARS-CoV-2 infection and increasing viral variants in children and young adults with impaired humoral immunity,” medRxiv, March 2021, link.

Summary:

• This study describes three patients with acute lymphoblastic leukemia who were persistently positive for SARS-CoV-2 by PCR. Specimens from all 3 patients were collected and used to detect SARS-CoV-2 RNA over the course of 6 months. Whole-genome sequencing and serological studies were performed to measure viral evolution and evidence of immune escape.
• Patient 1 is a previously healthy female under 5 years of age. Patient 2 is in the 20–25-year age range who was previously diagnosed with B-cell all six months prior to his SARS-CoV-2 positive test. Patient 3 is under 5 years of age who was diagnosed with high-risk B-cell all seven months prior to presentation to the ED with fever and confirmed positive for SARS-CoV-2 upon admission.
• Researchers found ongoing replication and infectivity for up to 162 days.
  • Viral load in patient 1 was highest at day 0 and then gradually declined and was last reliably detected on day 46.
  • Viral load in patient 2 remained consistent though day 172; SARS-CoV-2 was recovered by viral culture for up to day 144.
  • Viral load in patient 3 also remained consistent through day 162 despite weak seroconversion on day 83, and finally tested negative on day 196.

7. Yan et al., “Characteristics of Viral Shedding Time in SARS-CoV-2 Infections: A Systematic Review and Meta-Analysis, Frontiers of Public Health, March 2021, link.

Summary:

• Literature review looking at studies that measured viral shedding time (time to last positive PCR/negative PCR for SARS-CoV-2). They looked at 35 studies published through Oct 25, 2020. They pooled data from these studies and found that the pooled mean viral shedding is 16.8 days (95% confidence interval 14.8 to 19.4). This is much longer than the CDC’s guidance that allows “alternatives” to release isolation at 7 (with test) or 10 days (no test), depending on symptoms.
  • Respiratory tract specimens: 17.5 days pooled mean viral shedding time
  • Upper respiratory tract specimens: 17.5 days pooled mean viral shedding time
  • Stool specimens: 30.3 days pooled mean viral shedding time

8. Arnaout et al., “The Limit of Detection Matters: The Case for Benchmarking Severe Acute Respiratory Syndrome Coronavirus 2 Testing,” Clinical Infectious Diseases, February 2021, link.

Summary:

• Study looked at 4774 patients’ viral loads and test limit of detection. “The diagnostic priorities in the COVID-19 pandemic are to robustly identify 3 populations: the infected, the infectious, and the susceptible. Our study addresses the first of these. Specifically, it illustrates the clinical and epidemiologic impact of assay LoD [limit of detection] on SAR-CoV-2 diagnosis and the challenges of interpreting and comparing molecular assay results across various platforms. First, viral loads vary widely among infected individuals, from individuals with extremely high viral loads (potential “superspreaders”) who presumably would be picked up by even the least sensitive assays, to those whose viral loads are near, at, or even below the LoD of many assays. Therefore, a substantial fraction of infected patients will be missed by less sensitive assays. Concerningly, some of these missed patients are, have been, or will become infectious, and such misses will undermine public health efforts and put patients and their contacts at risk. This must give pause in the rush to approve additional testing options and increase testing capacity and emphasizes the importance of defining infectivity as a function of viral load and other factors (e.g., time of exposure), which remains a critical unknown in this pandemic. The relative ability of different sampling techniques to obtain specimens with the highest viral loads may also substantially impact detection rate.”

9. Baang et al., “Prolonged Severe Acute Respiratory Syndrome Coronavirus 2 Replication in an Immunocompromised Patient,” The Journal of Infectious Diseases, January 2021, link.

Summary:

• This study demonstrated ongoing replication of infectious SARS-CoV-2 for at least 119 days from an immunocompromised patient through viral cultures and sequencing analysis. “This case highlights challenges in managing immunocompromised hosts, who may act as persistent shedders and sources of transmission.”

10. Aydillo et al., “Shedding of Viable SARS-CoV-2 after Immunosuppressive Therapy for Cancer,” New England Journal of Medicine,” December 2020, link.

Summary:

• Researchers used cell cultures to detect viable virus in serially collected nasopharyngeal and sputum samples obtained from 20 immunocompromised patients who had Covid-19. Live virus was isolated in Vero cells and genetic variants were identified by whole-genome sequencing.
• Of the 20 patients, 15 were receiving active treatment or chemotherapy. 11 had severe Covid-19.
• A total of 78 samples were collected from the 20 patients. Viral RNA was detected for up to 78 days after symptom onset (interquartile range, 24 to 64 days). Viable virus was detected in 10 of 14 nasopharyngeal samples that were available from the first day of lab testing. Follow-up samples obtained from 5 patients grew virus in culture for 8, 17, 25, 26, and 61 days after symptom onset.

11. Li et al., “Prolonged shedding of severe acute respiratory syndrome coronavirus 2 in patients with Covid-19,” Emerging Microbes & Infections, December 2020, link.

Summary:

• Researchers monitored the clinical characteristics and virological features of 38 patients with Covid-19 (long-term carriers) who recovered from the acute disease, but still shed viral RNA for over 3 months.
• The median carrying history of the long-term carriers was 92 days after the first admission, and the longest carrying history was 118 days.
• Infectious SARS-CoV-2 was isolated from the sputum, where high level viral RNA was found. All nine full-length genomes of samples obtained in March–April 2020 matched early viral clades circulating in January–February 2020, suggesting that these patients persistently carried SARS-CoV-2 and were not re-infected. IgM and IgG antibodies and neutralizing-antibody profiles were similar between long-term carriers and recovered patients with similar disease courses.

12. Avanzato et al., “Case Study: Prolonged Infectious SARS-CoV-2 Shedding from an Asymptomatic Immunocompromised Individual with Cancer,” Cell, November 2020, link.

Summary:

• Case study of a 71-year-old immunocompromised patient who was infected with Covid-19 for at least 105 days, and infectious for at least 70 days. The patient remained asymptomatic throughout the course of the infection.
• “Given that immunocompromised individuals could have prolonged shedding and may not have typical symptoms of Covid-19, symptom-based strategies for testing and discontinuing transmission-based precautions, as recommended by the CDC, may fail to detect whether certain individuals are shedding infectious virus.”

13. Fontana et al., “Understanding viral shedding of severe acute respiratory coronavirus virus 2 (SARS-CoV-2): Review of current literature,” Cambridge University Press, October 2020, link.

Summary:

• Researchers analyzed 77 studies on SARS-CoV-2. All studies reported PCR-based assessments of viral shedding and 12 also included viral culture data.
• Among 28 studies, the overall pooled median duration of RNA shedding from respiratory sources was 18.4 days.
• When stratified by disease severity, the pooled median duration of viral RNA shedding from respiratory sources was 19.8 days among severely ill patients and 17.2 days in mild-to-moderate illness.
• Viable virus was isolated by culture from 6 to 20 days relative to symptom onset.

14. Jeong et al., “Viable SARS-CoV-2 in various specimens from Covid-19 patients,” Clinical Microbiology and Infection, July 2020, link.

Summary:

• Researchers collected nasopharyngeal swabs, saliva, urine and stool samples from 5 Covid-19 patients. Samples were tested by PCR; positive samples were subjected to virus isolation in Vero cells. Urine and stool samples were used to intranasally inoculate ferrets and evaluated the virus titres in nasal washes on 2-, 4-, 6- and 8-days post infection.
• All samples were positive by PCR. Viable virus was recovered from nasopharyngeal swabs and saliva samples. Viable virus was also recovered from ferrets’ nasal washes.
• Authors conclude: “Viable SARS-CoV-2 virus was demonstrated in saliva, urine, and stool from COVID19 patients up until days 11 to 15 of the clinical course. This result suggests that viable SARS-CoV-2 can be secreted in various clinical samples as well as respiratory specimens.” In particular, note the timeframe here – patients may be infectious for longer than the 10 days the CDC says.

Optimal PPE, including, a powered air-purifying respirator, coveralls that are impervious to viral penetration, head and shoe coverings, and medical grade gloves, is important to protect nurses and other health care workers from exposure to SARS-CoV-2. At minimum, nurses and health care workers should have an N95 respirator, isolation gown, eye protection, and medical grade gloves when caring for a confirmed or possible Covid-19 patient.

15. Barros et al., “Effectiveness of Elastomeric Half-Mask Respirators vs N95 Filtering Facepiece Respirators During Simulated Resuscitation. A Nonrandomized Controlled Trial,” JAMA Network Open, March 2021, link.

Summary:

• Nonrandomized controlled trial of clinicians and HCWs working on Covid-19 units at the University of Virginia. Participants had either been assigned an FFR (filtering facepiece respirator, N95) or an EHMR (elastomeric half-mask respirator), fit-tested. The final analysis included 100 participants.
• FFRs were reprocessed and reused up to 6 times. Participants performed chest compressions on a dummy while Bitrex (bitter-tasting chemical used for fit-tests) was aerosolized into a fit-testing hood. Testing was stopped at 2 minutes or when the participant could taste/smell the Bitrex (meaning their respirator had failed).
  • 0% of participants wearing EHMRs detected Bitrex
  • 28.1% of participants wearing N95 FFRs detected Bitrex, at median 69 seconds (interquartile range 42 to 107 seconds). There was no association between type of N95 model (5 models were reported) and failure.
• “Our results suggest that FFR fit during CPR is poor and that EMHRs provide superior fit, confirming previous research. We chose to evaluate fit during CPR because it is highly aerosolizing, physically strenuous, and has been associated with occupational transmission. Strengths of our study include our real-world design and prospective data collection. Limitations include the lack of blinding or randomization and the use of participant-reported detection. The data suggest that the EMHR is more effective at preventing aerosol inhalation during strenuous clinical work and should be considered for preventing Covid-19 transmission.”

16. Baffoe-Bonnie et al., “Filtration evaluation of expired elastomeric P-100 filter cartridges after months of real-world use during the COVID-19 pandemic,” Infection Control & Hospital Epidemiology, March 2021, link.

Summary:

• Study evaluated filtration efficacy of elastomeric respirator filters that had been used by direct care clinicians. Three pairs of P100 filters that had been in use for 5 or 6 months were tested. The filters had been used by 1 respiratory therapist, 1 progressive care nurse, and 1 medical intensive care nurse. Used cartridges were compared to new (unopened, unused) from the same batch of the Strategic National Stockpile. These cartridges were expired and been shown in previous studies to provide similar efficacy to an N95.
  • Cleaning protocol was to wipe down the outer casing of the filters with pre-moistened quarternary ammonium/isopropyl alcohol wipes between patients. Up to 10 times per day.
  • At the end of a shift, the wiped filter pair was disassembled from the mask, which underwent further cleaning.
  • Users reported no observed changes in breathability. No external damage to the filters was reported, except for wear and tear of cartridge label.
  • Filtration efficiencies of elastomeric filters used for 5 months (respiratory therapist) and 6 months (progressive care unit), as well as the control (unused filters), were mostly >95% across particle sizes. The filtration efficiency of filters used for 6 months (intensive care unit) was 90-95% but not statistically significantly different from the control filters.
• “We caution that these findings may not be applicable to nonexpired filters, but intuitively suspect that the duration of use could be longer.”

17. Jung et al., “Fit-failure rate associated with simulated reuse and extended use of N95 respirators assessed by a quantitative fit test,” Infection Control & Hospital Epidemiology, January 2021, link.

Summary:

• Study from South Korea looking at fit of N95s under reuse or extended use policies. 10 female infection control practitioners participated. Quantitative fit tests performed in accordance with OSHA’s standards and fit factor was calculated (fit factor of >100 is considered passing). Only looked at 3M 1870+. They performed 2 experiments of 1-hour multiple donnings with the same respirator, and one single 3-hour donning session, and one single 1-hour and 2-hour donning sessions. Participants were not performing clinical care while N95s were donned- they performed typical infection control duties including sitting at a desk, phone calls, talking to each other, and walking around wards. If fit failures occurred, they were refit with investigator assistance and refit tests were performed.
  • (reuse) repeat 1-hour donnings: all participants passed fit test at baseline. 60% participants failed fit test after 2 consecutive 1-hour donnings. 70% failed after 3 consecutive 1-hour donnings. 90% failed after 4 consecutive 1-hour donnings.
  • (extended use) repeat 3-hour donning: all participants passed at baseline. 50% of participants failed fit test after the first 3-hour donning.70% of participants failed fit test after the second 3-hour donning.
• “These data suggest that the extended use or reuse of N95 respirators due to the shortage of N95 respirators and other practical issues should be done with caution, especially in high-risk settings such as those involving aerosol-generating procedures. Therefore, more short-term use or other strategies such as powered air-purifying respirators (PAPR) should be considered in these circumstances.”
• Limitations:
  • Study was performed with infection control practitioners- “The activity of healthcare workers caring for patients with COVID-19 may be greater than that of infection practitioners and thus associated with higher rates of fit failure.”
  • Only 10 female Asian subjects. Only 1 model of N95

18. NIOSH – Filtering Facepiece Respirators with an Exhalation Valve: Measurements of Filtration Efficiency to Evaluate Their Potential for Source Control, December 2020, link.

Summary:

• “The findings in this report are based on tests of 13 FFR models from 10 different manufacturers. These findings show that FFRs with an exhalation valve provide respiratory protection to the wearer and can also reduce particle emissions to levels similar to or better than those provided by surgical masks, procedure masks, or cloth face coverings.”

19. Khonyongwa et al., “Incidence and outcomes of healthcare-associated COVID-19 infections: significance of delayed diagnosis and correlation with staff absence,” The Journal of Hospital Infection, October 2020, link.

Summary:

• Hospital in London identified hospital-acquired vs community-acquired Covid-19 in patients, from March 1 to April 18. Hospital-acquired Covid-19 was defined as: alternative etiology for symptoms upon admission, development of Covid symptoms more than 14 days after admission, or positive RNA respiratory sample more than 14 days after admission.
• All patients with symptoms matching Covid-19 were tested, all patients reviewed daily for symptoms. Patients were separated between Covid and non-Covid wards depending on test at admission, though sometimes when wards were full, “cohort” areas separated by curtains were established. Separate area for donning and doffing PPE was established for each ward. Staff wore FFP3 masks “as appropriate” (not defined).
• 7.1% of Covid patients admitted were classified as hospital-acquired and 3.7% as indeterminate (not positive on admission but before 14 days). Hospital-acquired Covid population was more likely to be more than 65 years, less likely to be Black Asian and Minority Ethnic (BAME), diabetes, CKD, malignancy, and others listed in the paper. There were no differences in outcomes.
• Self-reported staff sickness significantly correlated with weekly incidence of hospital acquired Covid cases.
• “Our results also suggest that 34.5% of all HA-COVID-19 and late indeterminate infections could be traced back to cases where the acquisition was from a community case, but an RNA based diagnosis could not be made within 48h of admission.”

20. Glasbey et al., “Elective Cancer Surgery in COVID-19–Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study,” Journal of Clinical Oncology, October 2020, link.

Summary:

• International multicenter study of adults undergoing elective surgery for solid cancer types in areas impacted by the Covid-19 pandemic.
• Each patient was classified as undergoing surgery in Covid-free surgical pathway or with no defined pathway. Covid-free surgical pathway was if complete segregation in all 3 areas (OR, critical care, and inpatient ward) away from patients with Covid. Only patients without a positive test or CT scan at time of surgery were included in study. A total of 9,171 patients from 445 hospitals were included in the study.
• Patients who had surgery when OR, critical care, and inpatient units were separated between Covid and non-Covid patients had lower rates of complications, lower rates of postop SARS-CoV-2 infection, and lower 30-day mortality rates than patients care for in mixed ORs/critical care/inpatient units.

21. Liu et al., “Protecting Healthcare Workers Amid the Covid-19 Crisis: A Safety Protocol in Wuhan,” Frontiers in Public Health, October 2020, link.

Summary:

• This study outlines successful safety measures that were adopted in an orthopedic department in Wuhan, China, in which none of the HCWs or their families contracted SARS-CoV-2.
• Their protocol covered five aspects:
  1. safety protection classification, including infection control measures and PPE including N95 respirator, eye protection, gown, gloves, and shoe and head coverings for patient care.
  2. reasonable working hours, including health care workers in quarantine area were limited to 3-hour shifts,
  3. ward protection, including splitting up the ward into three distinct sections for Covid quarantine, buffer, and clean zones with multiple measures to stop cross-contamination from occurring,
  4. operating room protection, and
  5. rest area protection

22. Ambrosch et al., “Effect of a strict hygiene bundle for the prevention of nosocomial transmission of SARS-CoV-2 in the hospital: a practical approach from the field,” Journal of Infection and Public Health, October 2020, link.

Summary:

• Paper reports on a study conducted retrospectively at a hospital in Bavaria, Germany, March 1 to June 10 (905 bed hospital).
• Patients were tested for SARS-CoV-2 based on respiratory symptoms, fever, and other symptoms (including taste and smell disturbances) or contact with a Covid-19 case. If one of the criteria was identified, the patient was classified as potentially infectious and separated in an isolation area. All possible and confirmed Covid patients were placed in a separate isolation area and each patient was isolated in a single room or cohorted. Staff wore FFP2 respirators, safety goggles, protective gowns and gloves. Visitors were not allowed. Universal masking was introduced March 26. Patients were daily evaluated for symptoms and all suspected patients were transferred to the isolation ward for testing.
• Nosocomial infections defined as positive PCR test more than 6 days after hospitalization. 10 nosocomial cases were identified out of 5081 patients not considered suspected/confirmed at admission.
• After introducing daily screening of all inpatients and universal masking, nosocomial rate decreased almost 80%. It should be noted that the hospital only identified 5 nosocomial Covid cases before the introduction of these additional measures. The study did not screen for asymptomatic nosocomial cases

23. Maltezou et al., “Hospital factors associated with SARS-CoV-2 infection among healthcare personnel in Greece,” The Journal of Hospital Infection, October 2020, link.

Summary:

• Report on Covid-19 infections among health care providers in 224 hospitals in Greece (126 are public, the rest are private or military). 13 tertiary care hospitals and 1 pediatric were designated as Covid-19 referral hospitals, 3 more were added later in the epidemic (total of 17 Covid hospitals).
• Confirmed patients requiring hospitalization were transferred to a Covid referral hospital. Health care providers caring for suspected or confirmed Covid patients wore FFP2 respirators, gloves, goggles or face shield, and gown resistant to fluid penetration. FFP3 was recommended for aerosol-generating procedures. Surgical masks were used during shortages.
• Health care providers who were exposed were tested upon development of symptoms though sometimes asymptomatic exposed HCPs were also tested. Health care providers included all staff in hospitals regardless of patient contact.
• From Feb 26 to May 3, 2020: 1,287 Covid-19 patients were hospitalized, and 158 health care providers were infected in public hospitals. Health care providers were statistically significantly more likely to be infected in non-Covid hospitals. Covid hospitals had significantly higher staffing, significantly more Covid patients.

24. Park et al., “Mass screening of healthcare personnel for SARS-CoV-2 in the Northern Emirates,” Journal of Hospital Infection, October 2020, link.

Summary:

• Hospital in UAE invited healthcare personnel (HCP) to screen for SARS-CoV-2 three times between April 2 and May 14, regardless of symptoms. HCP were also tested if they developed suspicious symptoms or had close contact with Covid patients. Contact tracing followed a confirmed case in HCP.
• All staff wore masks from March 12, no visitors starting March 24, all patients admitted to negative pressure rooms first after PCR test for SARS-CoV-2 from April 13. Covid patients were transferred to Covid hospital immediately. Patient-facing staff wore N95s, face shields, gowns, and gloves until patients had 2 consecutive negative Covid tests.
• Screening found few cases among the non-support staff- indicating these infection control measures were effective.
• 98% of the cases identified were among support staff, who were much more likely to share accommodation and commuter vehicles. “As the travel ban and lockdown had been imposed since late March 2020 in the UAE, a high incidence of COVID-19 in support staff might be related to share accommodation and crowded commuter vehicles…. Most migrant workers in Gulf countries are confined to small rooms which are shared up to a dozen workers.”

25. Piapan et al., “Covid-19 outbreak in healthcare workers in hospitals in Trieste, North-east Italy,” The Journal of Hospital Infection, August 2020, link.

Summary:

• Article describes health care worker infections in a region of Italy where health care workers accounted for 16.2% of all Covid infections in this province.
• The authors identify four main outbreaks/case clusters that contributed to high infection rate in health care workers, which were caused by:
  • Index patient without respiratory symptoms
  • 2 patients not suspected to be Covid+ at first
  • Community-acquired infection in HCW led to coworker infections
• Identifies (without significant detail) that asymptomatic cases and not recognizing Covid-positive quickly patients upon admission and health care worker meetings (which reportedly occurred with limited/no PPE) as key places of transmission in their hospitals.

26. Zhan et al., “Lesson learned from China regarding use of personal protective equipment,” American Journal of Infection Control, August 2020, link.

Summary:

• Hospitals in Hubei Province adopted World Health Organization (WHO) PPE protocols for Ebola. The article details PPE and protocols around entering and exiting locked designated Covid-19 units. As a result of the level-3 protection protocols combined with admitting patients to only Covid-19 designated hospitals, the number of health care workers infected declined significantly.

27. Bhaskar and Arun, “SARS-CoV-2 Infection Among Community Health Workers in India Before and After Use of Face Shields,” JAMA, August 2020, link.

Summary:

• Community health workers in India conducting home visits to follow up with asymptomatic family contacts of COVID+ patients
• First phase: community health workers wore surgical masks, gloves, and shoe covers, asked family members to wear masks and stay 6 feet apart during home visits
  • 2 workers developed symptoms, prompting testing of all workers (62), 19% were positive
• Second phase: added face shields to the PPE ensemble
  • No workers develop symptoms
  • (note that the paper states that no workers tested positive, but they only were referred for testing if developed symptoms vs the first phase where all were tested)
• Face shields may have some added benefit, though unclear of what type (face shields are NOT respiratory protection, but could help reduce contact with eyes/mucous membranes/contamination of mask)

28. Tong et al., “Surveillance of SARS-CoV-2 infection among frontline health care workers in Wuhan during COVID-19 outbreak,” Immunity, Inflammation and Disease, August 2020, link.

Summary:

• 222 health care workers traveled to Wuhan to support outbreak response
• 14-day quarantine upon return, throat swabs taken on day 3 and day 14 of quarantine, CT scans on day 14, antibody tests also conducted. All tests negative.
• Protections implemented:
  • Detailed donning and doffing PPE procedures/training
  • PPE: N95 respirator, coverall gown, goggle/face shield, and gloves
  • 4-6 hour shifts in contaminated area
  • Psychological and nutritional support

29. Oksanen et al., “Healthcare workers’ high COVID-19 infection rate: the source of infections and potential for respirators and surgical masks to reduce occupational infections,” medRxiv, August 2020, link.

Summary:

• Study reporting on healthcare worker exposures and infections at hospital in Finland
• 866 healthcare workers (majority nurses) filled out questionnaire on PPE use, exposure, etc. All participants with symptoms were tested- 4.7% were positive.
• 13 infections were confirmed from workplace exposure, 9 likely. 80% of exposure from patients happened in normal or cohorted ward. Lots of other data in the paper.
• Of HCW infections confirmed to result from workplace exposures, 0% reported wearing an FFP2/3 (N95 equivalent) respirator at time of exposure vs the remainder reported wearing a surgical mask (69.2%) or no mask (30.8%) at time of exposure.
• Same for HCW infections likely to result from workplace exposure, 0% reported wearing an FFP2/3 (N95 equivalent) respirator at time of exposure vs the remainder reported wearing a surgical mask (55.6%) or no mask (44.4%) at time of exposure.

30. Zhu and Zong, “Why did so few healthcare workers in China get COVID-19 infection,” QJM An International Journal of Medicine, August 2020, link.

Summary:

• This article is a summary of the main tenets of the response in China that protected health care workers and led to few health care worker infections.
• Five points that they highlight:
  1. universal masking of HCWs in healthcare settings at early stage.
  2. quick steps to secure supply of PPE and remedy shortage.
  3. higher standard of protection: “The main difference is that we used fluid-resistant protective clothing (coverall) with long sleeve and conjoined cap rather than uncapped isolation garment, as well as use respirators (i.e., N95 or European Union standard FFP2) rather than medical surgical masks, in wards dedicated for Covid-19 patients. A respirator, double rubber gloves, eye protection (i.e., goggles or a face shield), coverall and shoe covers were the standard equipment in contacting with Covid-19 patients in China."
  4. patients centralized at designated hospitals in China by national policy, hospitals had designated isolation wards.
  5. stringent lockdowns and community measures limited community transmission.

31. Nguyen et al., “Risk of Covid-19 among front-line health-care workers and the general community: a prospective cohort study,” The Lancet Public Health, July 2020, link.

Summary:

• This study examined the risk of Covid-19 among healthcare workers compared to the general public as well as the effect of personal protective equipment (PPE) on risk.  Researchers used the Covid Symptom Study app which asked daily questions about symptoms, testing, PPE, and exposures.
• They found that frontline healthcare workers with inadequate PPE caring for confirmed Covid-19 patients had 5.91x higher risk of a positive test when compared to healthcare workers with adequate PPE not caring for confirmed Covid-19 patients.  

32. Xue, Ming et al., “Beyond the PPE shortage: Improperly fitting personal protective equipment and Covid-19 transmission among health care professionals,” Hospital Practice, July 2020, link.

Summary:

• Report on three healthcare provider infections possibly caused by ill-fitting masks in a New Jersey hospital. Three healthcare providers worked on a COVID-19 inpatient floor, all three failed fit tests that were performed after the healthcare provider was tested or became symptomatic for COVID-19. The report does not trace conduct genetic sequencing but does underline the risks when hospitals do not conduct fit testing to ensure that N95 respirators properly fit staff.

33. Marago, Italo and Minen, Isa. “Hospital-Acquired Covid-19 Infection – The Magnitude of the Problem,” The Lancet Infectious Diseases, July 2020, link.

Summary:

• This study examined the prevalence of hospital-acquired Covid-19 infection or nosocomial transmission to patients in England. Patients were divided into two groups (nosocomial vs community). Cases were nosocomially acquired if a patient developed symptoms 7 or more days after hospital admission. Cases were community-acquired if a patient developed symptoms 7 days before hospital admission.
• Researchers found that 16.2% of Covid-19 patients met the criteria for nosocomial infection, the majority of which occurred in “low-risk wards” (suspected and negative Covid-19 zones).

34. Houlihan et al., “Pandemic peak SARS-CoV-2 infection and seroconversion rates in London frontline health-care workers,” The Lancet, July 2020, link.

Summary:

• This study examined a prospective cohort study of 200 frontline healthcare workers to evaluate risks.
• Researchers found that 44% of frontline healthcare workers had evidence of SARS-CoV-2 infection either by RT-PCR or serology in London. Evidence of infection among healthcare workers was more than double that of the London population, which highlights the importance of implementing policies to better protect healthcare workers.

35. Chen et al., “To Protect Healthcare Wokers Better, To Save More Lives with Covid-19,” Anesthesia & Analgesia,” July 2020, link.

Summary:

• This paper reported on healthcare worker protections in China during the early part of the pandemic in 2020. Three phases were reported-
  • First stage: It was unknown that a virus was the cause of the pneumonia cluster and healthcare workers were not protected. At this time, the infection rate ranged from 3.5% to 29% among healthcare workers in different hospitals in the epicenter of Wuhan.
  • Second stage: Health care workers had inadequate protection due to supply shortages. During this stage, the number of confirmed cases in China was still increasing rapidly. By February 11, 2020, a total of 1,716 health care workers were confirmed with COVID-19, including five deaths.
  • Third stage: disease severity acknowledged, the novel coronavirus had been identified, supply shortages were rapidly fixed thru increased manufacturing, and healthcare workers were fully protection. The highest level of precaution, so called “full precaution,” is mandatory for high-risk exposure, included a disposable surgical cap, test-fit N95 masks or respirators, gloves, goggles or face shield, gown and fluid-resistant shoe covers. “We would like to point out that the key element of full precaution is the complete coverage of the head and facial skin, which does not necessarily mean a conjoined hood or even powered air-purifying respirator system as previously reported.” No healthcare worker infections reported in this period.

36. Hou et al., “Personnel protection strategy for healthcare workers in Wuhan during the COVID-19 epidemic,” Precision Clinical Medicine, July 2020, link.

Summary:

• Serological testing of healthcare workers deployed to Wuhan to assist during surge.
• Zero of the healthcare workers deployed to Wuhan tested positive by serology after the end of their deployment. Compared to 3.4% of local Wuhan healthcare workers in isolation areas and 5.4% of local Wuhan healthcare workers in non-isolation areas.
• This study reports on PPE only and the results are indicative (healthcare workers with level 2/3 PPE had much lower infection rates- this level of PPE includes N95 FFR, disposable caps, isolation gowns (fluid repellant), goggles and face shield, shoe covers). But we know that there were other controls in place that could have impacted these rates including designated “fever hospitals” or units, designated dorms for the assisting healthcare workers, shorter shifts in isolation wards in some hospitals, etc.

37. Touati et al., “Prevention of nosocomial transmission of SARS-CoV-2 using pre-operative chest CT: a monocentric study during the outbreak,” The Journal of Hospital Infection, July 2020, link.

Summary:

• Reported on implementation of screening all patients before procedures using RT-PCR and chest CT at hospital in France. In addition to other preventive measures at the facility (social distancing, handwashing, PPE included gloves, goggles, face shields and masks, screening using temperature).
• Patients screened on the day before their procedure was scheduled if it could not be delayed. This led to a 7.5% change in the way that patients were handled (details not provided).
• Mean infection rate of staff decreased before vs after implementation of pre-op patient screening.

38. Chalikonda et al., “Implementation of an Elastomeric Mask Program as a Strategy to Eliminate Disposable N95 Mask Use and Resterilization: Results from a Large Academic Medical Center,” Journal of the American College of Surgeons, June 2020, link.

Summary:

• This article describes the results from a Pennsylvania hospital system’s widespread implementation of elastomeric and powered air purifying respirators (PAPR) program to alleviate the issues with N95 reusage and resterilization. Researchers reported on their phased-in process, training, education, and fit testing. After conducting a conservative cost analysis, they found that implementation of the elastomeric and PAPR program was 10x cheaper per month than an N95 reuse and decontamination program.

39. Degesys et al., “Correlation Between N95 Extended Use and Reuse and Fit Failure in an Emergency Department,” JAMA, June 2020, link.

Summary:

• This study examined the prevalence of N95 fit test failure while reusing 2 common types of N95 respirators at the University of California, San Francisco.
• Researchers found thatN95s worn for more hours were more likely to fail fit testing (p<0.05), N95s used for more shifts were more likely to fail fit testing (p<0.001), andN95s donned and doffed more times were more likely to fail fit testing (p<0.001).

40. Jung, Jiwon et al., “Contamination of personal protective equipment by SARS-CoV-2 during routine care of patients with mild Covid-19,” Journal of Infection, June 2020, link.

Summary:

• Healthcare workers wore N95 or PAPR, face shield, double gloves, boots, coveralls for 4 hours while providing patient care to patients with mild Covid-19 (no aerosol-generating procedures performed)
• Total of 133 surface samples taken from different parts of PPE ensemble. The following areas were positive for SARS-CoV-2 RNA:
  • 26% top of head
  • 26% top of foot
  • 16% sole of foot
  • 5% wrist
  • 5% abdomen
• “Therefore, our data support the wearing of PPE that fully cover the head and feet, as well as cautious doffing procedures."

41. Kim et al., “How South Korea Responded to the Covid-19 Outbreak in Daegu,” NEJM Catalyst, June 2020, link.

Summary:

• This article described how health officials in Daegu, South Korea adopted a comprehensive package or interventions that relieved shortages, concentrated resources, isolated cases, and protected health care workers.
• Key steps included:
  • Four-category risk stratification system (asymptomatic to mild, moderate, severe and critical)
  • Rapid expansion of beds for isolation with use of portable negative pressure machines
  • Recruitment of health care workers for both public health and medical responses. Shift lengths were closely monitored to minimize health care worker fatigue and infection risks.
  • Strict screening procedures at hospital entrances were implemented. Hospital wards, emergency departments and screening clinics were organized to screen, triage and separate suspected and confirmed cases of Covid-19 in order to avoid nosocomial infections and cross-contamination.
  • Universal mask policy and comprehensive use of PPE (N95 respirators, eye protection, shoe covers and coveralls). ICU hospital staff wore powered air-purifying respirators, shoe covers and coveralls.
  • Screening and exposure management of hospital staff, regardless of symptoms. Health care workers were asked to self-quarantine if they had close contact with a Covid-19 patient without proper PPE, if they had traveled internationally, or if they were part of a specific religious group known to have a high incidence of infection. On the 13th day of quarantine after exposure, health care workers were tested and could return to work only on day 15 after testing negative.

42. Feldman et al., “Exposure to a Surrogate Measure of Contamination from Simulated Patients by Emergency Department Personnel Wearing Personal Protective Equipment,” JAMA, April 2020, link.

Summary:

• This study assessed the protection of health care workers wearing the recommended PPE (N95 respirators, eye protection, isolation gowns, and gloves) while caring for a simulated patient with respiratory distress.
• Participating health care workers performed care tasks commonly required by patients with Covid-19 (e.g., airway management and ventilatory support) in a simulation. A nonvisible fluorescent compound as a marker of contamination was applied on predetermined surface areas (around the nose and mouth, palms, and upper chest) of the manikin and was added to the simulated secretion areas.
• Despite personal protective equipment, 7 of 8 participants had contamination (fluorescent markers) on their exposed skin. All participants had contamination in their hair; half had contamination on their shoes.

43. Wang, Xinghuan et al., “Association between 2019-nCoV transmission and N95 respirator use,” The Journal of Hospital Infection, March 2020, link.

Summary:

• This study examined the infection rate in two groups of departments. Three departments were in the “mask group” because they utilized N95 respirators and also frequently performed hand hygiene (respiratory, ICU, and Infectious Disease). Three departments were in the “non-mask group” because early in the outbreak they hadn’t implemented precautions- staff did not wear masks and disinfected and cleaned hands “occasionally.”
• There were significantly more confirmed or probable Covid-19 patients cared for in the departments in the “mask group,” meaning workers in those units had significantly more exposure than the “non-mask group.” “Mask group” reported statistically significantly fewer infections than the “non-mask group.” Mask group actually reported 0 infections. They found similar results in two other hospitals- staff wearing N95s and frequently conducting hand hygiene were not infected.

Separate and dedicated Covid-19 units, including no mixed  assignments, are important elements of an infection control plan.

44. Liu et al., “Protecting Healthcare Workers Amid the Covid-19 Crisis: A Safety Protocol in Wuhan,” Frontiers in Public Health, October 2020, link.

Summary:

• This study outlines successful safety measures that were adopted in an orthopedic department in Wuhan, China, in which none of the HCWs or their families contracted SARS-CoV-2.
• Their protocol covered five aspects:
  1. safety protection classification, including infection control measures and PPE including N95 respirator, eye protection, gown, gloves, and shoe and head coverings for patient care.
  2. reasonable working hours, including health care workers in quarantine area were limited to 3-hour shifts,
  3. ward protection, including splitting up the ward into three distinct sections for Covid quarantine, buffer, and clean zones with multiple measures to stop cross-contamination from occurring,
  4. operating room protection, and
  5. rest area protection

45. Glasbey et al., “Elective Cancer Surgery in COVID-19–Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study,” Journal of Clinical Oncology, October 2020, link.

Summary:

• International multicenter study of adults undergoing elective surgery for solid cancer types in areas impacted by the Covid-19 pandemic.
• Each patient was classified as undergoing surgery in Covid-free surgical pathway or with no defined pathway. Covid-free surgical pathway was if complete segregation in all 3 areas (OR, critical care, and inpatient ward) away from patients with Covid. Only patients without a positive test or CT scan at time of surgery were included in study. A total of 9,171 patients from 445 hospitals were included in the study.
• Patients who had surgery when OR, critical care, and inpatient units were separated between Covid and non-Covid patients had lower rates of complications, lower rates of postop SARS-CoV-2 infection, and lower 30-day mortality rates than patients care for in mixed ORs/critical care/inpatient units.

46. Wang et al., “Environmental virus surveillance in the isolation ward of COVID-19,” The Journal of Hospital Infection, April 2020, link.

Summary:

• This study evaluated the sites of environmental contamination on a Covid-19 isolation ward. The isolation ward was divided into three zones (clean zone, contaminated zone, and semi-contaminated zone) with two access points for patients and medical staff, respectively. Viral nucleic acid tests were performed on each ward. Health care workers took strict personal protective equipment and disinfection before entering and leaving the contaminated zone.
• Nucleic acid detection was positive in six (7.1%) locations. In the semi-contaminated zone, three sites had positive SARS-CoV-2, including the surface of the drawer in the nurse station, washstand and the drawer in the treatment room. In the contaminated zone, no sites in the patient room tested positive but one PDA was positive for the virus. In the clean zone, two sites had positive virus detection, namely the surface of the telephone receiver in the physician office and a push button of the water-free hand sanitizer.

All patients should be screened for Covid-19, considering diagnostic testing results, signs and symptoms, and recent exposure history.

47. Burns et al., “Casting the net wide: Universal testing of emergency admissions for SARS-CoV-2 to prevent onward transmission,” The Journal of Hospital Infection, November 2020, link.

Summary:

• Report from 1 hospital in Ireland. ED admissions with suspected Covid are assigned to Covid pathway with infection prevention precautions. Where Covid is not suspected (no symptoms or contact), a non-covid pathway is assigned with multiple occupancy (unless other infection prevention needs exist).
• Daily onsite testing began March 16 using PCR tests, including 1 rapid test. Universal admission testing began June 1. Contacts of Covid cases identified among patients and staff were tested on day 0 and 7 and staff were advised to remain off work 14 days and patients were isolated or cohorted with other contacts for 14 days.
• 3,393 PCR tests performed June 1 o Sept 30 on non-suspected Covid patients. 9 were positive (0.26%).
• After implementation of universal admission testing, number of staff contacts was reduced, and number of patient contacts was reduced.

48. Khonyongwa et al., “Incidence and outcomes of healthcare-associated COVID-19 infections: significance of delayed diagnosis and correlation with staff absence,” The Journal of Hospital Infection, October 2020, link.

Summary:

• Hospital in London identified hospital-acquired vs community-acquired Covid-19 in patients, from March 1 to April 18. Hospital-acquired Covid-19 was defined as: alternative etiology for symptoms upon admission, development of Covid symptoms more than 14 days after admission, or positive RNA respiratory sample more than 14 days after admission.
• All patients with symptoms matching Covid-19 were tested, all patients reviewed daily for symptoms. Patients were separated between Covid and non-Covid wards depending on test at admission, though sometimes when wards were full, “cohort” areas separated by curtains were established. Separate area for donning and doffing PPE was established for each ward. Staff wore FFP3 masks “as appropriate” (not defined).
• 7.1% of Covid patients admitted were classified as hospital-acquired and 3.7% as indeterminate (not positive on admission but before 14 days). Hospital-acquired Covid population was more likely to be more than 65 years, less likely to be Black Asian and Minority Ethnic (BAME), diabetes, CKD, malignancy, and others listed in the paper. There were no differences in outcomes.
• Self-reported staff sickness significantly correlated with weekly incidence of hospital acquired Covid cases.
• “Our results also suggest that 34.5% of all HA-COVID-19 and late indeterminate infections could be traced back to cases where the acquisition was from a community case, but an RNA based diagnosis could not be made within 48h of admission.”

49. Piapan et al., “Covid-19 outbreak in healthcare workers in hospitals in Trieste, North-east Italy,” The Journal of Hospital Infection, August 2020, link.

Summary:

• Article describes health care worker infections in a region of Italy where health care workers accounted for 16.2% of all Covid infections in this province.
• The authors identify four main outbreaks/case clusters that contributed to high infection rate in health care workers, which were caused by:
  • Index patient without respiratory symptoms
  • 2 patients not suspected to be Covid+ at first
  • Community-acquired infection in HCW led to coworker infections
• Identifies (without significant detail) that asymptomatic cases and not recognizing Covid-positive quickly patients upon admission and health care worker meetings (which reportedly occurred with limited/no PPE) as key places of transmission in their hospitals.

50. Touati et al., “Prevention of nosocomial transmission of SARS-CoV-2 using pre-operative chest CT: a monocentric study during the outbreak,” The Journal of Hospital Infection, July 2020, link.

Summary:

• Reported on implementation of screening all patients before procedures using RT-PCR and chest CT at hospital in France. In addition to other preventive measures at the facility (social distancing, handwashing, PPE included gloves, goggles, face shields and masks, screening using temperature).
• Patients screened on the day before their procedure was scheduled if it could not be delayed. This led to a 7.5% change in the way that patients were handled (details not provided).
• Mean infection rate of staff decreased before vs after implementation of pre-op patient screening.

Contact tracing and testing are essential to effective Covid-19 infection control plans.

51. Chin et al., “Frequency of Routine Testing for Coronavirus Disease 2019 (Covid-19) in High-risk Healthcare Environments to Reduce Outbreaks,” Clinical Infectious Diseases, October 2020, link.

Summary:

• Modelling study that estimates the impact of frequent surveillance testing of health care workers on health care transmission. It is a basic model that gives us an estimation of the impact.
• In an ideal case with zero delay in test results and perfect sensitivity of test, daily testing of health care workers reduced R by 98.9%.
• Longer test result delays of 3 to 5 days reduced daily testing impact from 85.3% to 56.5% and 25.9%, respectively, reduction in R.
• Optimal testing frequency was dependent on baseline R. Higher the R, the more frequent testing would need to occur to be effective.
• Assuming other measures are implemented, and R is 1.5, testing weekly would suffice to bring R below 1.

52. Rivett L, et al., “Screening of healthcare workers for SARS-CoV-2 highlights the role of asymptomatic carriage in Covid-19 transmission,” eLife, May 2020, link.

Summary:

• “Significant differences exist in the availability of healthcare worker (HCW) SARS-CoV-2 testing between countries, and existing programmes focus on screening symptomatic rather than asymptomatic staff. Over a 3-week period (April 2020), 1,032 asymptomatic HCWs were screened for SARS-CoV-2 in a large UK teaching hospital. Symptomatic staff and symptomatic household contacts were additionally tested. Real-time RT-PCR was used to detect viral RNA from a throat + nose self-swab. 3% of HCWs in the asymptomatic screening group tested positive for SARS-CoV-2. 17/30 (57%) were truly asymptomatic/pauci-symptomatic. 12/30 (40%) had experienced symptoms compatible with coronavirus disease 2019 (COVID-19) >7 days prior to testing, most self-isolating, returning well. Clusters of HCW infection were discovered on two independent wards. Viral genome sequencing showed that the majority of HCWs had the dominant lineage B∙1. Our data demonstrates the utility of comprehensive screening of HCWs with minimal or no symptoms. This approach will be critical for protecting patients and hospital staff.”

53. Scwierzeck V, König JC, Kühn J, et al. 2020. “First Reported Nosocomial Outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in a Pediatric Dialysis Unit,” Clinical Infectious Diseases, April 2020, link.

Summary:

• “Person-to-person transmission was at the heart of a hospital outbreak of SARS-CoV-2 between healthcare workers (HCWs) and patients in the pediatric dialysis unit at the UHM. Semi quantitative real-time RT-PCR results suggest that individuals with high viral load pose a risk to spread SARS-CoV-2 in the hospital setting. Our epidemiological observation highlights the need to develop strategies to trace and monitor SARS-CoV-2 infected HCWs in order to prevent COVID-19 outbreaks in the hospital setting.”

Surgical and cloth masks do not provide respiratory protection to the wearer. A minimum of N95 respirators is necessary to protect nurses and health care workers caring for patients with confirmed or possible Covid-19. Surgical and cloth masks may be useful for source control as they are intended to protect others from the wearer’s large respiratory droplet emissions. However, unlike N95 respirators, surgical masks are not required to be fit tested, which means that air (potentially carrying infectious particles) can leak around the edges of the mask. Surgical and cloth masks are also not made of materials that are good filters. In contrast, N95s and other respirators are subjected to rigorous filter certification by the U.S. National Institute for Occupational Safety and Health (NIOSH), which ensures they filter at least 95% of very small airborne particles or higher.

54. MacIntyre CR, et al., “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare Workers,” BMJ Open, March 2015, link.

Summary:

• This study compared the efficacy of cloth masks to medical masks among healthcare workers in 14 hospitals in Vietnam. A total of 1,607 participants were randomized by ward into three arms: (1) medical masks at all times on their work shift; (2) cloth masks at all times on shift or (3) control arm (standard practice, which may or may not include mask use). The control arm was ‘standard practice’, which comprised mask use in a high proportion of participants.
• There were three primary end points: 1) Clinical respiratory illness; 2) influenza-like illness (ILI), defined as fever ≥38°C plus one respiratory symptom and (3) laboratory-confirmed viral respiratory infection.
• The rates of all infection outcomes were highest in the cloth mask arm, with the rate of influenza-like illness (ILI) statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm.
• An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group.
  • Penetration of cloth masks by particles was almost 97% and medical masks 44%. Cloth masks resulted in significantly higher rates of infection than medical masks, and also performed worse than the control arm.

55. “Covid-19 shortages of masks and the use of cloth masks as a last resort,” – a follow-up by the authors to the above article, published on March 30, 2020, link.

• “We recommend that health workers should not work during the Covid-19 pandemic without respiratory protection as a matter of work health and safety. In addition, if health workers get infected, high rates of staff absenteeism from illness may also affect health system capacity to respond...For Covid-19, wearing a mask is not enough to protect health care workers – use of gloves and goggles are also required as a minimum, as SARS-CoV-2 may infect not through the respiratory route, but also through contact with contaminated surfaces and self-contamination.”

56. Rengasamy et al., “Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles,” The Annals of Occupational Hygiene, June 2010, link.

Summary:

• Household fabric materials and cloth masks were challenged with polydisperse as well as monodisperse particles in the 20–1000 nm size range, which include the size of many viruses and initial penetration levels measured and compared with those values obtained for N95 respirator filter media.
• Researchers found that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels against polydisperse NaCl aerosols employed in the NIOSH particulate respirator test protocol at 5.5 cm s−1. Similarly, varying levels of penetrations (9–98%) were obtained for different size monodisperse NaCl aerosol particles in the 20–1000 nm range.
• Results obtained in the study show that common fabric materials may provide marginal protection against nanoparticles including those in the size ranges of virus-containing particles in exhaled breath.

57. Rengasamy et al., “Filtration Performance of FDA-Cleared Surgical Masks,” Journal of the International Society for Respiratory Protection, July 2009, link.

Summary:

• This study investigated the filtration performance of surgical masks for a wide size range of submicron particles including the sizes of many viruses. Five models of FDA-cleared surgical masks were tested for room air particle penetrations at constant and cyclic flow conditions.
• Researchers found that many surgical masks are made of materials ineffective at filtration, with some models letting through up to 88% of particles.

58. Oberg, Tara and Lisa Brosseau, “Surgical mask filter and fit performance,” American Journal of Infection Control, May 2008, link.

Summary:

• This study evaluated the filter performance and facial fit of a sample of surgical masks. Filter penetration was measured for at least 3 replicates of 9 surgical masks using monodisperse latex sphere aerosols (0.895, 2.0, and 3.1 μm) at 6 L/min and 0.075-μm sodium chloride particles at 84 L/min. Facial fit was measured on 20 subjects for the 5 masks with lowest particle penetration, using both qualitative and quantitative fit tests.
• All 20 subjects failed the unassisted qualitative fit test on the first exercise (normal breathing). Eighteen subjects failed the assisted qualitative fit tests; 60% failed on the first exercise. Quantitative fit factors ranged from 2.5 to 9.6.
• None of the surgical masks exhibited adequate filter performance and facial fit characteristics to be considered respiratory protection devices.

1. Truong et al., “Persistent SARS-CoV-2 infection and increasing viral variants in children and young adults with impaired humoral immunity,” medRxiv, March 2021, link.

Summary:

• This study describes three patients with acute lymphoblastic leukemia who were persistently positive for SARS-CoV-2 by PCR. Specimens from all 3 patients were collected and used to detect SARS-CoV-2 RNA over the course of 6 months. Whole-genome sequencing and serological studies were performed to measure viral evolution and evidence of immune escape.
• Patient 1 is a previously healthy female under 5 years of age. Patient 2 is in the 20–25-year age range who was previously diagnosed with B-cell all six months prior to his SARS-CoV-2 positive test. Patient 3 is under 5 years of age who was diagnosed with high-risk B-cell all seven months prior to presentation to the ED with fever and confirmed positive for SARS-CoV-2 upon admission.
• Researchers found ongoing replication and infectivity for up to 162 days.
  • Viral load in patient 1 was highest at day 0 and then gradually declined and was last reliably detected on day 46.
  • Viral load in patient 2 remained consistent though day 172; SARS-CoV-2 was recovered by viral culture for up to day 144.
  • Viral load in patient 3 also remained consistent through day 162 despite weak seroconversion on day 83, and finally tested negative on day 196.

2. Buonsenso et al., “Preliminary Evidence on Long COVID in children,” medRxiv, January 2021, link.

Summary:

• Researchers in Italy tracked 129 children diagnosed with Covid-19 between March and November 2020 (mean age of 11 ± 4.4 years, 62 (48.1%) female).
• More than half reported at least one persisting symptom even after 120 days since Covid-19, with 42.6% being impaired by these symptoms during daily activities. Symptoms like fatigue, muscle and joint pain, headache, insomnia, respiratory problems and palpitations were particularly frequent, as also described in adults.

3. Mehta et al., “SARS-CoV-2 (COVID-19): What Do We Know About Children? A Systematic Review,” Clinical Infectious Diseases, December 2020, link.

Summary:

• Researchers conducted a systematic review and narrative synthesis of all literature relating to SARS-CoV-2 in pediatric populations. A total of 24 studies relating to Covid-19 were included in the review.
• They found that children are infected at approximately the same rate as adults. Though many children may be asymptomatic or too mildly infected to register as positive on some diagnostic tests, thus limiting case detection of children.

4. Laws et al., “Symptoms and Transmission of SARS-CoV-2 Among Children — Utah and Wisconsin, March–May 2020,” Pediatrics, December 2020, link.

Summary:

• Researchers conducted a household transmission investigation during March to May in Milwaukee, Wisconsin, and Salt Lake City, Utah. The study enrolled individuals with Covid-19 and their household contacts, assessed daily symptoms prospectively for 14 days, and obtained specimens for SARS-CoV-2 PCR and serology testing. Among 58 households, 188 contacts were enrolled (120 adults; 68 children).
• They found that children in both states were just as likely as adults to become infected with Covid-19 within their households, and while kids spread the virus in one fifth of homes, their lack of severe symptoms may have allowed their infections to otherwise escape detection.
  • Nineteen of the 68 pediatric contacts (28%) tested positive for SARS-CoV-2, while 36 of the 120 adult contacts (30%) tested positive, including 18 of 65 (28%) in homes with children and 18 of 55 (33%) without them.
  • Covid-19 transmission from children to adults may have occurred in 2 of 10 households (20%) with susceptible household members, and children may have spread the virus to other children in 1 of 6 homes with potential child-to-child spread (17%).

5. Sharma et al., “Reversible Myocardial Injury Associated With SARS-CoV-2 in an Infant,” Journals of the American College of Cardiology, December 2020, link.

Summary:

• Case report of a reversible myocardial injury and acute decompensated heart failure associated with documented SARS-CoV-2 infection in a 2-month-old infant. The patient presented with an episode of choking and cyanosis after feeding. There was no history of fever, cough, upper respiratory tract infection symptoms, diarrhea, vomiting, or decreased oral intake prior to the initial presentation.
• The 2-month-old patient initially tested negative for SARS-CoV-2, but repeat PCR was positive. He was infected by a visiting family member the week prior to presentation.

6. King et al., “Symptoms associated with a positive result for a swab for SARS-CoV-2 infection among children in Alberta,” Canadian Medical Association Journal, November 2020, link.

Summary:

• Researchers analyzed results for 2,463 children who underwent testing for SARS-CoV-2 infection between April 13 and September 30, 2020, in Alberta.
  • Of 2,463 children tested, 1,987 had a positive result and 476 had a negative result.
  • Of children with a positive test result for SARS-CoV-2, 714 (35.9%) were asymptomatic. The symptoms most strongly associated with a positive test were fever (25.5%), cough (24.5%), and runny nose (19.3%).
  • Cough and runny nose were also common in SARS-CoV-2–negative patients and were not predictive of a positive result; neither were sore throat, nasal congestion, or diarrhea. Loss of taste or smell, however, was highly predictive, with a likelihood of test positivity more than seven times higher than that for patients without this symptom. Other symptoms predictive of a positive result included nausea and vomiting, headache, sneezing, and fever.
  • When the researchers combined loss of taste/smell, nausea/vomiting, and headache symptoms, the overall likelihood was highly predictive of a positive result, but the infrequency of loss of taste/smell in children may limit its predictive value.

7. García-Salido et al., “Severe manifestations of SARS-CoV-2 in children and adolescents: from COVID-19 pneumonia to multisystem inflammatory syndrome: a multicentre study in pediatric intensive care units in Spain,” Critical Care, November 2020, link.

Summary:

• Researchers compared the cases of pediatric patients with SARS-CoV-2 infection and clinical symptoms consistent with MIS-C to those with SARS-CoV-2 infection not fulfilling MIS-C criteria. Forty-seven PICUs (pediatric ICU), including 1st, 2nd and 3rd level of care, from every region of Spain participated in the Registry. Between March 1st and June 15th, 2020, a total of 74 children admitted to the participating PICUs were included in the Registry, with ages ranging from 15 days to 16.5 years.
  • MIS-C seems to be the most frequent presentation among critically ill children with SARS-CoV-2 infection. MIS-C patients are older and usually healthy. They show a higher prevalence of gastrointestinal symptoms and shock and are more likely to receive vasoactive drugs and immunomodulators and less likely to need mechanical ventilation than non-MIS-C patients.
  • Sixty-one percent met MIS-C definition. MIS-C patients were older than non-MIS-C patients: 9.4 years vs 3.4 years. A higher proportion of them had no previous medical history of interest (88.2% vs 51.7%). Non-MIS-C patients presented more frequently with respiratory distress (60.7% vs 13.3%). MIS-C patients showed higher prevalence of fever (95.6% vs 64.3%), diarrhea (66.7% vs 11.5%), vomits (71.1% vs 23.1%), fatigue (65.9% vs 36%), shock (84.4% vs 13.8%) and cardiac dysfunction (53.3% vs 10.3%).

8. Slaats et al., “Case report of a neonate with high viral SARSCoV-2 loads and long-term virus shedding,” Journal of Infection and Public Health, October 2020, link.

Summary:

• Case report of a 7-day-old neonate who was hospitalized in the Netherlands with Covid-19. The patient had high SARS-CoV-2 viral load and prolonged shedding. Monitoring the course of this infection showed that SARS-CoV-2 RNA was detectable in the nasopharynx until day 19 and in stool until day 42 after symptom onset.

9. Ahmed et al., “Multisystem inflammatory syndrome in children: A systematic review,” EClinicalMedicine, September 2020, link.

Summary:

• Researchers conducted a systematic review which summarizes the clinical presentation of MIS-C from 662 patients. They found that MIS-C can develop 3 to 4 weeks without warning healthy children after asymptomatic infections.
  • Of the 662 patients, almost 90% underwent an echocardiogram due to significant cardiac manifestation of the disease.
  • Researchers note that some children will need lifelong monitoring and interventions due to the extent of cardiac damage.

10. Park YJ et al., “Contact Tracing during Coronavirus Disease Outbreak, South Korea, 2020,” Emerging Infectious Diseases, July 2020, link.

Summary:

• Researchers identified 5,706 people who were the first to report Covid-19 symptoms in their households between January 20 and March 27, 2020, when schools were closed, and then traced the 59,073 contacts of these “index cases.” They tested all of the household contacts of each patient, regardless of symptoms, but only tested symptomatic contacts outside the household.
• Researchers found:
  • Children between 10 and 19 years can transmit the virus as effectively as adults.
  • Children < 9 years were about half as likely as adults to transmit. Note that fewer than 30 positive cases were included in this age group. It is possible that children in this age group may have had fewer contacts due to stay-at-home orders in the beginning of the pandemic but not because they’re less likely to transmit.

11. Heald-Sargent et al., “Age-Related Differences in Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Levels in Patients with Mild to Moderate Coronavirus Disease 2019 (COVID-19),” JAMA Pediatrics, July 2020, link.

Summary:

• Researchers examined real-time PCR cycle threshold (CT) values from nasopharyngeal swabs from 145 patients Covid-19, within 1 week of symptom onset. They compared three groups: a) young children younger than 5 years, b) older children aged 5 to 17 years, and c) adults aged 18 to 65 years.
• They found that young children had significantly lower median (interquartile range) CT values, indicating that young children have equivalent or more viral nucleic acid in their upper respiratory tract compared with older children and adults. Children < 5 years had 10 to 100 times more SARS-CoV-2 viral RNA in their upper respiratory tract than older kids and adults.

1. Whitaker et al., “Persistent symptoms following SARS-CoV-2 infection in a random community sample of 508,707 people,” Imperial College of London, July 2021, link.

Summary:

• Researchers from Imperial College of London estimated symptom prevalence and investigated co-occurrence of symptoms among 508,707 participants reporting symptoms lasting 12 weeks or more following suspected or confirmed Covid-19. Data from random community-based samples of the population in England were analyzed, collected between September 2020 and February 2021.
• Researchers found that 37.7% of participants who had Covid-19 experienced at least one symptom lasting 12 weeks or more, while 14.8% experienced three or more symptoms for at least 12 weeks. Individuals with persistent symptoms at 12 weeks fell into two groups:
  • Group 1 – respiratory symptoms such as shortness of breath, tight chest and chest pain were the most common, with more people reporting that they had severe symptoms.
  • Group 2 – fatigue-related symptoms such as tiredness with muscle aches and difficulty sleeping were the most common.
• The prevalence of persistent symptoms was 1.5 times higher in women than men.

2.  Vanichkachorn et al., “Post COVID-19 Syndrome (Long Haul Syndrome): Description of a Multidisciplinary Clinic at the Mayo Clinic and Characteristics of the Initial Patient Cohort,” Mayo Clinic Proceedings, May 2021, link.

Summary:

• This study reported on the first 100 patients who were evaluated and treated in Mayo Clinic’s Covid-19 Activity Rehabilitation program (CARP) between June 1 and December 31, 2020. Patients were evaluated a mean of 93 days after initial infection.
• Of the 100 patients in the study, 80% reported unusual fatigue, 59% had respiratory and neurologic complaints. More than one-third reported difficulties with performing basic daily living activities; only 1 in 3 had returned to unrestricted work activity. Most patients had no preexisting comorbidities prior to SARS-CoV-2 infection, and many did not experience symptoms that were severe enough to require hospitalizations.

3. Taquet et al., “6-month neurological and psychiatric outcomes in 236,379 survivors of Covid-19: a retrospective cohort study using electronic health records,” The Lancet Psychiatry, May 2021, link.

Summary:

• Researchers analyzed electronic health records of 81 million U.S. patients (both insured and uninsured patients). They compared a cohort of Covid survivors to matched control cohorts (1 – patients diagnosed with influenza; 2 – patients diagnosed with respiratory tract infections). The Covid cohort was divided into subgroups of hospitalized and non-hospitalized patients.
• Among 236,379 patients who had been diagnosed with Covid-19, 1 in 3 patients experienced a psychiatric or neurological illness in 6 months following a Covid diagnosis, with 12.8% receiving their first such diagnosis. Most diagnostic categories were more common in patients who had Covid-19 than in those who had influenza and those who had other respiratory tract infections.

4. Havervall et al., “Symptoms and Functional Impairment Assessment 8 Months After Mild Covid-19 Among Health Care Workers,” JAMA, April 2021, link.

Summary:

• Researchers investigated Covid related long-term symptoms in relatively young, healthy health care workers in Sweden from April 2020 to January 2021. They collected blood samples every 4 months and administered questionnaires.
• Of the 323 seropositive participants, 26% of those who had mild COVID-19 reported at least one moderate to severe symptom that lasted more than 2 months, compared to 9% of participants without Covid.
  • 11% of those with mild Covid-19 had at least one debilitating symptom that lasted for at least 8 months, compared to 2% of the seronegative group.
  • 15% reported their long-term symptoms (lasting at least 8 months) moderately to markedly disrupted their social life, compared with 6% of the seronegative participants.

5. Al-Aly, Z., Xie, Y. & Bowe, “High-dimensional characterization of post-acute sequalae of Covid-19,” Nature, April 2021, link.

Summary:

• This study analyzed over 73,000 Veterans Health Administration users who had Covid-19 and nearly 5 million VHA users who did not have Covid and were not hospitalized.
• Researchers found that Covid survivors had higher risk for death and health care utilization beyond 30 days after illness. They also found that individuals who had Covid and were not hospitalized reported excess negative health impacts over at least 6 months and that affected nearly every organ and regulatory system in the body.
• They also found increased incident use of opioids and non-opioids, antidepressants, anxiolytics, antihypertensives, and oral hypoglycemics and evidence of laboratory abnormalities in multiple organ systems.

6. Davis et al., “Characterizing Long Covid in an International Cohort: 7 Months of Symptoms and Their Impact,” medRxiv, April 2021, link.

Summary:

• Researchers analyzed responses from 3,762 participants with confirmed or suspected Covid-19, from 56 countries, with illness duration of at least 28 days.
• Of the 3,762 participants, 96% reported symptoms beyond 90 days. 45% reported requiring a reduced work schedule and 22% were not working at the time of survey due to health conditions.
• A total of 205 symptoms in 10 organ systems was identified, with 66 symptoms traced over seven months. Most commonly reported symptoms were fatigue, shortness of breath, headaches, dry cough, chest tightness and muscle aches.

7. Gaber et al., “Persistent post-covid symptoms in healthcare workers,” Occupational Medicine, April 2021, link.

Summary:

• Researchers investigated the long-term impact of Covid-19 in health care workers. Seropositivity for SARS-CoV-2 antibodies was evaluated for 3,759 health care workers in an English teaching hospital two months following the peak of the April 2020 wave. A questionnaire was sent electronically, which included questions about the respondents' demographics, acute symptoms and hospitalization, method of confirmation of the diagnosis, persistent symptoms, and their severity and if they sought medical help or had sick leave.  
• Of the 3,759 subjects tested for SARS-CoV-2 antibodies, 932 (24%) were positive; 138 health care workers responded to the questionnaire. 114 had confirmed Covid-19 via PCR during the acute illness or antibody test afterwards. 24 respondents believed they had Covid-19 but had no laboratory confirmation.
  • 45% of 138 health care workers who responded to the questionnaire reported persistent symptoms, with 32% struggling to cope 3–4 months following the peak of the wave.
  • Moderate-to-severe fatigue was the most disabling symptom (39%); mild-to-moderate shortness of breath, anxiety and sleep disturbance were almost universal.
  • Only 16% consulted their general practitioner about their symptoms with only 2% taking sick leave after recovering from the acute illness.

8. Johansson et al., “Long-Haul Post-Covid-19 Symptoms Presenting as a Variant of Postural Orthostatic Tachycardia Syndrome: The Swedish Experience,” JACC Case Reports, March 2021, link.

Summary:

• This case report presented the first case series of three Swedish patients diagnosed with postural orthostatic tachycardia syndrome (POTS) more than 3 months after initial Covid-19 infection. All three patients experienced flu-like symptoms; 2 out of the 3 patients tested negative for Covid.
• Symptoms suggestive of POTS included persistent fatigue, headache, palpitations, dizziness, brain fog, or exercise intolerance during recovery from Covid-19.

9. Huang et al., “COVID Symptoms, Symptom Clusters, and Predictors for Becoming a Long-Hauler: Looking for Clarity in the Haze of the Pandemic,” medRxiv, March 2021, link.

Summary:

• This study analyzed electronic medical records of 1,407 individuals in California who tested positive for Covid-19 and evaluated symptoms at presentation (days 0 – 10 following a Covid diagnosis) and at 61+ days.
• Researchers found that 27% reported persistent symptoms more than 60 days after initial infection. Five symptom clusters at day 61+ were identified: chest pain-cough, dyspnea-cough, anxiety-tachycardia, abdominal pain nausea, and low back pain-joint pain.
• Nearly one third of the patients were asymptomatic during their initial infection through the 10 days after they tested positive.

10. Nalbandian et al., “Post-acute Covid-19 syndrome,” Nature Medicine, March 2021, link.

Summary:

• This study comprehensively reviewed the current literature on post-acute Covid-19, its pathophysiology, and its organ-specific sequelae. They found that symptoms range from severe fatigue, cognitive dysfunction, gastrointestinal and musculoskeletal disorders to pulmonary and cardiovascular diseases.

11. Salmon-Ceron et al., “Clinical, virological and imaging profile in patients with prolonged forms of COVID-19: A cross-sectional study,” Journal of Infection, February 2021, link.

Summary:

• This study described the clinical, biological, and imaging profile of patients with initial mild to moderate Covid-19 infections.
• Of the 70 patients included in the study, 54.3% patients had symptoms that persisted from the 1st episode, 50% that disappeared and reappeared and 75.7% presented new symptoms that were absent during the 1st episode appeared. Most commonly reported symptoms were fever, anosmia, headaches and asthenia.

12. Taquet et al., “Bidirectional associations between COVID-19 and psychiatric disorder: retrospective cohort studies of 62,354 Covid-19 cases in the USA,” The Lancet Psychiatry, February 2021, link.

Summary:

• This study assessed whether a diagnosis of Covid-19 was associated with increased rates of subsequent psychiatric diagnoses, and whether patients with a history of psychiatric illness are at a higher risk of being diagnosed with Covid-19. Researchers looked at electronic health records in 54 health care organizations in the United States; a total of 62,354 Covid patients were included between January and August 2020.
• They found that Covid survivors have significantly higher rates of psychiatric diagnoses and psychiatric history is a potential risk factor for being diagnosed with Covid-19, independent of known physical risk factors.

13. Huang et al., “6-month consequences of Covid-19 in patients discharged from hospital: a cohort study,” The Lancet, January 2021, link.

Summary:

• This study investigated the long-term health consequences and associated risk factors of previously hospitalized Covid-19 patients, discharged between January 7, 2020, and May 29, 2020. Patients in the cohort study were interviewed, underwent physical exams, received blood tests, and performed 6-minute walking tests. A total of 1,733 patients were included. A follow-up study was conducted from June 16 to September 3, 2020; the median follow-up time after symptom onset was 186 days.
• Researchers found that at 6 months following initial infection, patients most frequently experienced fatigue, sleep difficulties, and anxiety or depression. Patients who were severely ill during hospital admission had more severe impaired pulmonary diffusion capacities and abnormal chest imaging manifestations.

14. Miglis et al., “A case report of postural tachycardia syndrome after Covid-19,” Clinical Autonomic Research, September 2020, link.

Summary:

• Case report of a previously healthy, 26-year-old ER nurse who developed postural orthostatic tachycardia syndrome (POTS) several months after symptom onset. The patient had no pre-existing symptoms of autonomic impairment.

1. Bernal et al., “Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant,” New England Journal of Medicine, July 2021, link.

Summary:

• This study estimated the effectiveness of the Pfizer and AstraZeneca Covid-19 vaccines against Delta (B.1.617.2) and Alpha (B.1.1.7) variants after one or two doses. Data on all symptomatic sequenced cases of Covid-19 in England from April 5 to May 16 were used to estimate the proportion of cases with either variant according to the patients’ vaccination status.
• Researchers found reduced vaccine effectiveness after a single dose of Pfizer or AstraZeneca Covid-19 vaccine.
  • Pfizer vaccine efficacy after one dose was 47.5% against Alpha and 35.6% against the Delta variant
  • AstraZeneca vaccine efficacy after one dose was 48.7% against Alpha and 30% against the Delta variant
• Researchers found modest differences in vaccine effectiveness after receipt of two vaccine doses
  • Pfizer vaccine efficacy after two doses was 93.7% against Alpha and 88% against the Delta variant
  • AstraZeneca vaccine efficacy after two doses was 74.5% against Alpha and 67% against the Delta variant

2. Fisman and Tuite, “Progressive Increase in Virulence of Novel SARS-CoV-2 Variants in Ontario, Canada,” medRxiv, July 2021, link.

Summary:

• This study analyzed the virulence of the Delta (B.1.617.2) SARS-CoV-2 variant relative to variants with N501Y mutation. Researchers created a retrospective cohort of patients testing positive for SARS-CoV-2 in Ontario and screened for variants of concern (VOC). Case information was extracted from the Ontario provincial Case and Contact Management (CCM) database. A total of 211,197 cases was included in the study, with episode dates between February 7 and June 22, 2021.
• Researchers found significant increases in the risk of hospitalization, ICU admission and death among Delta infections and N501Y-positive VOCs compared to non-VOCs.
  • The adjusted elevation in risk associated with N501Y-positive variants was 59% for hospitalization, 105% for ICU admission and 61% for death
  • The increase in risk associated with the Delta variant was significantly higher – 120% for hospitalization, 287% for ICU admission and 137% for death
• Researchers also found that individuals infected with VOCs were, on average, younger and less likely to have commodities than those infected with non-VOC SARS-CoV-2 strains.

3. Muecksch et al., “Longitudinal variation in SARS-CoV-2 antibody levels and emergence of viral variants: implications for the ability of serological assays to predict immunity,” medRxiv, July 2021, link.

Summary:

• This study measured antibodies in a cohort of 112 participants with a history of SARs-CoV-2 infection. Participants were surveyed to determine the date of the positive PCR test, the date of onset of symptoms, and if their symptoms required hospitalization. Serum samples were taken at a baseline visit (~3.5 to ~8.5 weeks post PCR test) and 2 weeks, 4 weeks, 8 weeks and 22 weeks later.
• Researchers found significantly reduced neutralization titers (2.5 to 5-fold reduction in sera from patients infected with Beta, Delta and Alpha variants with E484K) when compared to non-variants of concern strains.

4. Li et al., “Viral infection and transmission in a large well-traced outbreak caused by the Delta SARS-CoV-2 variant,” medRxiv, July 2021, link.

Summary:

• This study investigated the first local transmission of the Delta SARS-CoV-2 variant in Guangzhou, China, from the first index case identified on May 21, 2021, to the last case reported on June 18, 2021. Researchers measured and compared the relative viral loads of 62 patients infected with the Delta variant with viral loads of 63 patients infected with earlier strains.
• Viral loads in the Delta variant infections were 1,260 times higher than those infected with previous SARS-CoV-2 strains. Researchers also found that the interval time from exposure to PCR positive was shorter for Delta infections (4 days, peak at 3.71 days) compared to previous strains (6 days, peak at 5.61 days).
• The authors noted, “This highlights more infectiousness of Delta variant during the early stage of infection is very likely, and the frequency of the population screening should be optimized for the intervention. The more infectiousness of the Delta variant infections in pre-symptomatic phase highlights the need of timely quarantine for the suspicious infection cases or closely contacts before the clinical onset or the PCR screening.”

5. Farinholt et al., “Transmission event of SARS-CoV-2 Delta variant reveals multiple vaccine breakthrough infections,” medRxiv, July 2021, link.

Summary:

• This study describes a Delta variant transmission event among family members at a wedding ceremony in Texas. All 92 wedding guests were required to be fully vaccinated and took place outdoors in a large, open-air tent.
• Researchers identified a total of 6 individuals who were fully vaccinated with Pfizer, Moderna or Covaxin Covid-19 vaccines and tested positive for SARS-CoV-2. All 6 breakthrough infections were symptomatic; one developed severe Covid-19 and one died. Two members who travelled from India to attend the wedding tested negative for SARS-CoV-2 as part of the pre-flight criteria.

6. Wall et al., “Neutralising antibody activity against SARS-CoV-2 VOCs B.1.617.2 and B.1.351 by BNT162b2 vaccination,” The Lancet, June 2021, link.

Summary:

• This study examined the vaccine-induced antibody neutralizing capacity against Delta (B.1.617.2), Alpha (B.1.1.7) and other variants of concern. Researchers analyzed antibodies in the blood of 250 participants who received either one or two doses of the Pfizer Covid-19 vaccine, up to three months after the first dose.
• Researchers found that fully vaccinated individuals had a 5.8-fold reduction in neutralizing antibodies against the Delta SARS-CoV-2 variant when compared to the wild-type strain, upon which current Covid-19 vaccines are based. Single-dose vaccine recipients had significantly lower neutralizing antibody levels – 79% against the wild-type strain, 50% against the Alpha variant, and 32% against the Delta variant.

7. Planas et al., “Reduced sensitivity of SARS-CoV-2 variant Delta to antibody neutralization,” Nature, July 2021, link.

Summary:

• This study analyzed the sensitivity of the Delta (B.1.617.2), Alpha (B.1.1.7) and Beta (B.1.351) variants to monoclonal antibodies as well as the neutralization ability of sera from previously infected or vaccinated individuals.
• Researchers found the following:
  • Some monoclonal antibodies lost binding to the spike protein and no longer neutralized the Delta variant
  • Only 10 percent of the sera from single-dose (Pfizer or AstraZeneca) Covid-19 vaccine recipients neutralized the Delta variant. Administration of two vaccine doses generated a neutralizing response in 95% of individuals, with titers 3 to 5-fold lower against Delta than the Alpha variant.
• Sera from convalescent patients collected up to 12 months post onset of symptoms were 4-fold less potent against the Delta variant

8. Davis et al., “Reduced neutralisation of the Delta (B.1.617.2) SARS-CoV-2 variant of concern following vaccination,” medRxiv, June 2021, link.

Summary:

• This study compared neutralizing capacity of Pfizer-BioNTech (BNT162b2) and Oxford/AstraZeneca (ChAdOx1) Covid-19 vaccines against Delta (B.1.617.2) and Beta (B.1.351) variants, and the wild-type strain. Sera was collected from 156 healthy individuals who received either one or two doses of Pfizer, or one or two doses of AstraZeneca Covid-19 vaccines. Neutralizing antibodies were measured against HIV (SARS-CoV-2) pseudotype-based system.
• Researchers found lower neutralization efficacy against Delta and Beta variants:
  • Neutralizing efficacy was 4 to 6-fold lower against the Delta and Beta variants compared to the wild-type strain.
  • Pfizer Covid-19 vaccine showed a 11.30-fold reduction in antibody titer against the Delta variant and a 9.56-fold reduction against the Beta variant. The mean antibody titer induced by vaccination with two doses of AstraZeneca was significantly lower than that induced by two doses of Pfizer.