Face Masks May Reduce Covid-19 Spread

April 10, 2020

Social distancing, masks and eye protection all appear to reduce the spread of COVID-19 in health care facilities and the general community, according to a new review commissioned by the World Health Organization (WHO).

The review found that maintaining a distance of at least 3 feet (1 m) from others reduces the chance of contracting or spreading the coronavirus by 82%, and that maintaining a distance of 6 feet (2 m) may be more effective.

For the general public, wearing masks and cloth masks has also been associated with protection from COVID-19; this is also true for health care workers, but there is a trend that suggests N95 masks provide greater protection than other types of masks in the health care setting. The authors say that people may prefer protection for the eyes over the nose and mouth, and may also provide additional benefits in community and healthcare settings.

However, the authors point out that the findings on masks and eye protection are based on limited evidence. And in general, none of the practices examined in the studies completely prevented COVID-19.

“While distancing, masks, and eye protection were each highly protective, none of the practices completely protected individuals from [COVID-19] infection,” said lead study author Dr. Derek Chu, a clinical scientist in the Department of Health Research Methods, Evidence, and Impacts and the Department of Medicine at McMaster University in Ontario, in a statement. To that end, “basic measures such as hand hygiene are also key to curbing the current COVID-19 pandemic and future waves,” he said.

For this new commentary, published in The Lancet, Chu and his team examined research on COVID-19 and related conditions SARS and MERS. Overall, the researchers analyzed information from 44 studies from 16 countries, involving more than 25,000 people.

These studies examined the effects of social distance, masks, and eye protection (e.g., face shields, goggles, and eyeglasses) on the spread of the virus. The researchers considered these measures separately, rather than together. They were unable to examine how a person’s potential exposure time affects their risk of infection).

With social estrangement, the chance of contracting or spreading these coronaviruses was about 3 percent when people kept at least 3 feet away from others, compared to 13 percent when people kept less than this distance. What’s more, for every additional 3 feet (up to 10 feet, or 3 meters), the risk of contracting or spreading these coronaviruses is cut in half.

With a mask on, the chance of contracting or spreading them is 3 percent, compared to 17 percent without a mask, a reduction of more than 80 percent. And for eye protection, the chance of infection or transmission was 6 percent with protection and 16 percent without protection.

“Our findings are the first to synthesize all the direct information on COVID-19, SARS and MERS and provide the best available evidence on how best to use these common and simple interventions to help ‘flatten the curve,'” Holger Schünemann, senior study author and professor at McMaster University, said in a statement.

Other analyses in healthcare settings found that the N95 respirator was 96 percent effective in protecting workers in those settings, compared with 77 percent effectiveness for other types of masks, such as surgical masks.

These findings suggest that “for healthcare workers in COVID-19 wards, [N95] respirators should be the minimum standard of care,” wrote Raina MacIntyre, a professor of global biosafety at the Kirby Institute at the University of New South Wales in Australia, and colleagues in a commentary accompanying the study.

The review also “supports the universal use of face masks, as they are equally effective in healthcare and community settings,” the review said.

However, the review did not include any randomized controlled trials-the target criteria for medical research-in which people are randomly assigned to treatment or control groups. (There were no randomized controlled trials on this topic.) Instead, the review looked at observational studies in which the researchers looked at populations without assigning treatments. The authors say that randomized controlled trials are now needed, especially those that look at the effect of masks on the risk of infection; two such trials of masks are currently underway in Denmark and Canada.