<b>Background</b>: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread person-to-person  through  close  contact.  We  aimed  to  investigate  the  effects  of  physical  distance,  face  masks,  and  eye  protection on virus transmission in health-care and non-health-care (eg, community) settings.
<p><b>Methods</b>: We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses. We  obtained  data  for  SARS-CoV-2  and  the  betacoronaviruses  that  cause  severe  acute  respiratory  syndrome,  and  Middle  East  respiratory  syndrome  from  21  standard  WHO-specific  and  COVID-19-specific  sources.  We  searched  these data sources from database inception to May 3, 2020, with no restriction by language, for comparative studies and for contextual factors of acceptability, feasibility, resource use, and equity. We screened records, extracted data, and  assessed  risk  of  bias  in  duplicate.  We  did  frequentist  and  Bayesian  meta-analyses  and  random-effects  meta-regressions. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. This study is registered with PROSPERO, CRD42020177047.
</p><p><b>Findings</b>: Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25697 patients). Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m (n=10736,  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  (change  in  relative  risk  [RR]  2·02  per  m;  p<sub>interaction</sub>=0·041;  moderate  certainty).  Face  mask  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%,  –15·9  to  –10·7;  low  certainty),  with  stronger  associations  with  N95  or  similar  respirators  compared  with  disposable  surgical  masks  or  similar  (eg,  reusable  12–16-layer cotton masks; p<sub>interaction</sub>=0·090; posterior probability &gt;95%, low certainty). Eye protection also was 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).  Unadjusted studies and subgroup and sensitivity analyses showed similar findings.
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<b>Interpretation</b>: The findings of this systematic review and meta-analysis support physical distancing of 1 m or more and  provide  quantitative  estimates  for  models  and  contact  tracing  to  inform  policy.  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.Funding World Health Organization.
Derek K Chu, Elie A Akl, Stephanie Duda, Karla Solo, Sally Yaacoub, Holger J Schünemann, on behalf of the COVID-19 Systematic Urgent Review Group Effort (SURGE) study authors*
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