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Physical Distancing, Face Masks, and Eye Protection to Prevent Transmission of COVID-19
abstract
This abstract is available on the publisher's site.
Access this abstract now Full Text Available for ClinicalKey SubscribersBACKGROUND
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.
METHODS
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.
FINDINGS
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=25 697 patients). 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% 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; pinteraction=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; pinteraction=0·090; posterior probability >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.
INTERPRETATION
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 randomised 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.
Additional Info
Disclosure statements are available on the authors' profiles:
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 Jun 27;395(10242)1973-1987, DK Chu, EA Akl, S Duda, K Solo, S Yaacoub, HJ SchünemannFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Evidence for physical distancing, face masks, and eye protection.
Many of us watched in horror over the Memorial Day weekend while multitudes wantonly abandoned social distancing and masking and as states backed away from closures and imposition of nonpharmaceutical interventions (NPIs). Now, two weeks later—as experts predicted—we are seeing a significant rise in COVID-19 cases across the United States. This phenomenon brought back a passage from my favorite treatise of the 1918 influenza pandemic:
“Studying the record of the American people in 1918 and 1919 is like standing on a high hill and watching a fleet of many vessels sailing across a current of terrible power to which the sailors pay little attention. They grip their tillers firmly, peer at their compasses, and hold faithfully to courses, which, from their vantage, seem to be straight, but we can see that the secret current is sweeping them far downstream. The immense flow swamps many of the ships and their sailors drown, but the others take little notice. The other are intent on maintaining their own unwavering courses.”1
In this rapidly evolving pandemic, and in the absence of preventive vaccines and routinely available and effective therapeutics, it is incredibly important to assess the evidence for or against the use of three easily available NPIs: physical distancing, face masks, and eye protection. A recent systematic review and meta-analysis does just that, providing significant support for these public health measures.2
The authors identified 172 observational studies for the systematic review and a subset of 44 comparative studies for the meta-analysis. As with many of our public health interventions, no randomized controlled studies were available. I think the most important findings are summarized in the GRADE (Grading of Recommendations Assessment, Development and Evaluation) table:
Bottom line for clinicians: NPIs work. We do not know how well they work in combination with each other. We do not have high-quality randomized controlled trials. We do, however, have substantial evidence, and for now NPIs are all we have.
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