Effectiveness of Face Masks in Preventing COVID-19 Transmission in Real-World Settings: A Systematic Literature Review

Abstract Background. Since its emergence, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an unprecedented global pandemic. Evidence regarding the effectiveness of mask wearing is important to support guidelines for public health practice and implementation of infection-control strategies. Previous systematically reviews within controlled settings suggest wearing face masks are ‘efficacious’ at preventing COVID-19. However, a comprehensive review of the ‘effectiveness’ of face masks in preventing COVID-19 transmission in real-world settings is needed in order to generalize findings. The present study reviewed literature on the effectiveness of wearing face masks in preventing COVID-19 transmission in real-world settings. Methods. Following PRISMA guidelines, three databases and gray literature sources were searched up until January 2022. Inclusion criteria for studies were: 1) written in or translated into English; 2) assess the SARS-CoV-2 transmission; 3) assess the behavior of mask wearing and 4) study conducted in a non-laboratory-controlled setting (e.g., worksites, schools etc.). All 2,240 search results were reviewed for inclusion. Two reviewers extracted study characteristics. Three reviewers independently assessed quality of evidence and risk of bias using JBI critical appraisal tools. Results. This review identified 48 unique studies that met the criteria. Most studies investigated the effect of face masks in a healthcare setting (n=21, 43%). The majority (n=44; 91.6%) of studies showed that wearing face masks led to a reduction in transmission or risk of transmission of COVID-19, and the protective effect of masks was increased when combined with other preventive measures. The findings support that face masks may be up to 79% effective in preventing transmission in non-controlled real-life settings. Conclusions. The results of this systematic review strongly support public health recommendations for wearing a mask to reduce the risk of COVID-19 infection in real-world settings. Effective communication efforts are needed to inform the general public of the benefits of wearing face masks to prevent COVID-19.