Social distancing, face masks and eye protection work to prevent the spread of COVID-19, a new meta-analysis has found. 

Investigators performed a systematic review of 172 studies involving COVID-19, SARS, and MERS. The results are the “best available evidence” that infection risk from coronaviruses is dependent on the distance from an infected individual and the type of face mask and eye protection worn, they reported. 

Keeping one meter (3.3 feet) from others has a strong protective effect, and six feet is likely to be even more effective, the researchers found. In addition, single-layer cloth masks appear to offer less protection than surgical masks. And not surprisingly, N95 masks are the most protective. Wearing eye protection, such as goggles or glasses, is also helpful, they wrote.

None of these measures provided complete protection, however, and no randomized trials of these measures were found for any of the three coronaviruses studied.

“Optimum use of face masks, respirators, and eye protection in public and health-care settings should be informed by these findings and contextual factors,” concluded first author Derek K. Chu, from McMaster University, Canada.

Notably, most study participants found these personal protection strategies acceptable and reassuring, the researchers added. But they also noted challenges, including frequent discomfort and facial skin breakdown, and concerns about unequal resource use. There were also concerns about communication difficulties and the potential for perception of reduced empathy by those they were caring for.

The article was published Monday in The Lancet.