Face masks to prevent transmission of respiratory diseases: Systematic review and meta-analysis of randomized controlled trials*
AbstractObjectiveTo examine the effect of face mask intervention in respiratory infections across different exposure settings and age groups.DesignSystematic review and meta-analysis.Data sourcesPubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science were searched for randomized controlled trials investigating the effect of face masks on respiratory infections published by November 18th 2020. Our reporting follows the PRISMA guidelines.Eligibility criteria for selecting studiesRandomized controlled trials investigating the effect of face masks in respiratory infections and influenza-like illness across different exposure settings and age groups. Two reviewers independently performed the search, extracted the data, and assessed the risk of bias. A random effects meta-analysis with risk ratio, risk difference, and number needed to treat were performed. Findings in exposure settings, age groups, and role of non-compliance were examined using a subgroup analysis.ResultsTotal of 17 studies were included, with N = 11, 601 individuals in intervention and N = 10, 286 in the control group with follow-up duration from 4 days to 19 months). 14 trials included adults (and children) and 3 included children only. 12 studies suffered from non-compliance in the treatment arm and 11 in the control arm. All studies were intent-to-treat analyses, and, thus, non-compliance can bias individual intent-to-treat estimates towards zero. Four out of seventeen studies supported use of face masks. A meta-analysis of all 17 studies found no association between face mask intervention and respiratory infections (RR = 0.9046 [0.777 - 1.053], p = 0.196, p fixed effect = 0.0006). However, a meta-analysis using odds ratios adjusted for age, sex, and vaccination (when available) suggests protective effect of the face mask intervention (17 studies, OR = 0.850 [0.736 - 0.982], p=0.027). A subgroup meta-analysis among adults with (unadjusted) risk ratios found a decrease in respiratory infections (14 studies, RR = 0.859 [0.750 - 0.983], p = 0.026, and 4 studies with a combined face masks and hand hygiene intervention RR = 0.782 [0.696 - 0.879], p < 0.0001). Finally, the face mask use is also supported by a meta-regression adjusting the effect estimates for non-compliance in the controls (17 studies RR = 0.87 [0.780 - 0.980], p = 0.017).ConclusionOur findings support the use of face masks to prevent respiratory infections.