Face mask use in the Community for Reducing the Spread of COVID-19: a systematic review

BackgroundEvidence is needed on the effectiveness of wearing face masks in the community to prevent SARS-CoV-2 transmission. MethodsSystematic review and meta-analysis to investigate the efficacy and effectiveness of face mask use in a community setting and to predict the effectiveness of wearing a mask. We searched MEDLINE, EMBASE, SCISEARCH, The Cochrane Library and pre-prints from inception to 22 April 2020 without restriction by language. We rated the certainty of evidence according to Cochrane and GRADE approach. FindingsOur search identified 35 studies, including 3 randomised controlled trials (RCTs) (4017 patients), 10 comparative studies (18984 patients), 13 predictive models, 9 laboratory experimental studies. For reducing infection rates, the estimates of cluster-RCTs were in favour of wearing face masks versus no mask, but not at statistically significant levels (adjusted OR 0.90, 95%CI 0.78-1.05). Similar findings were reported in observational studies. Mathematical models indicated an important decrease in mortality when the population mask coverage is near-universal, regardless of mask efficacy. In the best-case scenario, when the mask efficacy is at 95%, the R0 can fall to 0.99 from an initial value of 16.90. Levels of mask filtration efficiency were heterogeneous, depending on the materials used (surgical mask: 45-97%). One laboratory study suggested a viral load reduction of 0.25 (95%CI 0.09-0.67) in favour of mask versus no mask. InterpretationThe findings of this systematic review and meta-analysis support the use of face masks in a community setting. Robust randomised trials on face mask effectiveness are needed to inform evidence-based policies. Fundingnone. PROSPERO registrationCRD42020184963. Contribution to the fieldGuidelines by various organizations provide conflicting evidence about the effectiveness of face mask use in the community. We performed a systematic review of the available evidence, including 35 studies, across 41 countries and six continents. Previous systematic reviews on the effectiveness of face mask use mainly focused on healthcare and household setting including only randomized controlled trials and observational studies with most of them of low quality. In our review, we included randomized controlled trials, observational studies, laboratory experimental studies as well as mathematical modelling studies in order to answer different questions and provide quantitative estimates for planning pandemic response efforts. Our review supports the use of surgical masks in the community for providing protection during the COVID-19 pandemic. However, the infection rate, mortality, spread of transmission (R0), filtering capacity of masks and viral load reduction are highly dependent on the type of face mask worn and on the adherence of the population wearing masks. Policy makers should promote face mask use in the community.