This systematic review and meta-analysis evaluated the available evidence to date regarding physical distancing, face masks, and eye protection to prevent spread of COVID-19.
The authors identified 172 observational studies across 16 countries and six continents, with no randomized controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25 697 patients). Within these studies, they found:
- Viral transmission was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m (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 increased as distance was lengthened (change in relative risk [RR] 2.02 per m)
- Face mask use could result in a large reduction in risk of infection (n=2,647; aOR 0.15, 95% CI 0.07 to 0.34, RD -14.3%, -15.9 to -10.7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar
- Eye protection also was associated with less infection (n=3,713; aOR 0.22, 95% CI 0.12 to 0.39, RD -10.6%, 95% CI -12.5 to -7.7; low certainty).
- Unadjusted studies and subgroup and sensitivity analyses showed similar findings
These findings suggest the use of non-pharmaceutical interventions, such as physical distancing of more than about 3 feet and wearing a medical mask and eye goggles, to reduce COVID-19 transmission. However the authors also note that the certainty of the evidence for face and eye mask protection is low and other measures, like physical distancing, are by far the most effective at reducing spread of coronavirus. They call for robust randomized trials and proper risk assessments of control measures, rather than casual assumptions.
An accompanying editorial highlights several of the review’s findings, including a subanalysis that found N95 respirators were 96% effective, considerably more so than other mask types.