Literature Review Examines SARS-CoV-2 Prevention Methods

While the exact transmission dynamics are unknown, SARS-CoV-2 is spread through close contact between persons.

The team behind a recent systematic review and meta-analysis published in The Lancet investigated the ideal physical distance for avoiding SARS-CoV-2 transmission and assessed the use of eye protection and face coverings in preventing acquisition.

The investigators evaluated information from 22 global databases concerning SARS-CoV-2 as well as the related viruses which cause SARS and MERS. The search identified more than 170 observational studies and 44 comparative studies, but no randomized clinical trials.

The results supported physical distancing when in public, as well as the use of face masks, but questions remain in the absence of randomized trials.

“Transmission of viruses was lower with physical distancing of 1 meter or more, compared with a distance of less than 1 meter (n=10 736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] −10·2%, 95% CI −11·5 to −7·5; moderate certainty); protection was increased as distance was lengthened,” the study authors wrote.

Face mask usage led to a large reduction in risk of infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD −14·3%, −15·9 to −10·7; low certainty). Stronger associations were found between protection and N95 respirators compared to surgical disposable masks or cloth masks.

Eye protection was also associated with fewer infections (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD −10·6%, 95% CI −12·5 to −7·7; low certainty).

“Optimum use of face masks, respirators, and eye protection in public and health-care settings should be informed by these findings and contextual factors. Robust randomized trials are needed to better inform the evidence for these interventions, but this systematic appraisal of currently best available evidence might inform interim guidance,” the study team wrote.

Results suggest that risk for infection is largely dependent on distance to the infected individual and modified by the type of face mask and/or eye protection used. Investigators praised current policies of 1 meter distance and encouraged concerned individuals to take a 2 meter distance when possible.

The data help move forward a debate which has changed over time on the use of masks in the community. It appears keeping a distance and wearing protective apparel is beneficial. But none of the methods assessed totally prevented infection. Other measures, such as vigorous hand hygiene, remain vitally important as well.

Skin damage has become common among health care workers using protective gear such as masks.

Michael B. Edmond, MD, MPH, MPA, MBA, associate chief medical officer, chief quality officer, and clinical professor of infectious diseases, University of Iowa Health Care, spoke with Contagion® about a viewpoint he and colleagues published in JAMA on the universal adopting of face shields to help cut the transmissibility of COVID-19.