In a systematic review and meta-analysis funded by the World Health Organization (WHO), Chu and colleagues investigated the optimum distance to avoid person-to-person virus transmission and the use of face masks and eye protection, given that severe acute respiratory syndrome coronavirus (SARS-CoV-2), which causes COVID-19, is spread though close contact in health care and non-health care settings.

Data for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the betacoronaviruses that cause severe acute respiratory syndrome and Middle East respiratory syndrome from 21 standard World Health Organization-specific and coronavirus disease-2019 (COVID-19)-specific sources were searched from database inception to May 3, 2020, for comparative studies and for contextual factors of acceptability, feasibility, resource use, and equity. The researchers did not restrict for language.

Records were screened, date extracted, and risk of bias in duplicate assessed. Frequentist and Bayesian meta-analyses and random-effects meta-regressions were performed. The certainty of evidence was measured according to Cochrane methods and the GRADE approach.

The researchers identified 172 observational studies across 16 countries and 6 continents, with 44 relevant comparative studies in health care and non-health care settings (n = 25,697 patients). There were no randomized controlled trials.

Transmission of viruses 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% confidence interval 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 (change in relative risk [RR], 2.02/m; P_interaction = 0.041; moderate certainty).

Facemask use could result in a large reduction in risk of infection (n = 2647; aOR, 0.15; 95% CI, 0.07 to 0.34; RD, -14.3%; 95% CI, -15.9 to -10.7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable 12- to 16-layer cotton masks; P_interaction = 0.090; posterior probability >95%, low certainty).

Eye protection was also associated with less infection (n = 3713; aOR, 0.22; 95% CI, 0.12 to 0.39; RD, -10.6%; 95% CI, -12.5 to -7.7; low certainty). Similar findings were shown in unadjusted studies and subgroup and sensitivity analyses.

The authors concluded that this study supports physical distancing of 1 m or more and provides quantitative estimates for models and contact tracing to inform policy. Optimum use of facemasks, 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 (See Chu DK, Akl EA, Duda S, et al. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet. 2020;395(10242):1973-1987. doi:10.1016/S0140-6736(20)31142-9.)

This study is registered with PROSPERO, CRD42020177047.