Effectiveness of face masks worn in community settings at reducing the transmission of SARS-CoV-2: a rapid review [version 1; peer review: 1 approved with reservations]

Background: The use of face masks is part of a suite of infection prevention and control measures intended to limit the transmission of respiratory viral diseases. The use of face masks by the general public has been subject to ongoing debate, with limited direct evidence on the effectiveness of face masks in the community during the COVID-19 pandemic. The aim of this review was to synthesise direct evidence on the effectiveness of wearing face masks at reducing the transmission of SARS-CoV-2 in community settings.
Methods: A rapid review was conducted. PubMed, Embase, NHS Evidence and Europe PMC were searched systematically from 1 January to 27 August 2020. Clinical trials, cohort, case control, and cross-sectional studies were included if they reported on the effectiveness of face masks in community settings at reducing the transmission of SARS-CoV-2. Studies were critically appraised and synthesised narratively.
Results:  Seven observational studies were identified, including one study set in households and six in community settings, that reported on the effectiveness of wearing face masks compared with not wearing face masks at reducing the transmission of SARS-CoV-2. Results suggested that face masks reduce the risk of SARS-CoV-2 infection; however, all studies were at high risk of bias and the quality of the evidence was low.
Conclusions: This is to date the most comprehensive review of direct evidence on the effectiveness of wearing face masks in the community during the COVID-19 pandemic. There is limited, low certainty direct evidence that wearing face masks reduces the risk of transmission of SARS-CoV-2 in community settings. Further high quality studies are required to confirm these findings.