Face masks prevent transmission of respiratory diseases: a meta-analysis of randomized controlled trials

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSObjectiveC_ST_ABSTo 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, and Web of Science were searched for randomized controlled trials investigating the effect of face masks on respiratory infections published by November 18th, 2020. We followed PRISMA guidelines. Eligibility criteria for selecting studiesRandomized controlled trials investigating face masks in respiratory infections across different exposure settings. Two reviewers performed the search, extracted data, and assessed the risk of bias. Random effects meta-analysis with risk ratio, adjusted odds ratios, and number needed to treat were performed. Findings by source control or wearer protection, age groups, exposure settings, and role of non-compliance were evaluated. ResultsSeventeen studies were included, (N=11,601 cases and N=10,286 controls, follow-up from 4 days to 19 months). Fourteen trials included adults and children and three trials included children only. Twelve studies showed non-compliance in treatment and eleven in control group. Four studies supported the use of face masks. Meta-analysis across all studies with risk ratios found no association with number of infections (RR=0.957 [0.810 - 1.131], p=0.608). Meta-analysis using odds ratios adjusted for age, sex, and vaccination (when available) showed protective effect of face masks (OR=0.850 [0.736 - 0.982], p=0.027). Subgroup meta-analysis with adjusted odds ratios found a decrease in respiratory infections among adults (14 studies, OR = 0.829 [0.709 - 0.969], p=0.019) in source control setting (OR = 0.845 [0.7375 - 0.969], p=0.0159) and when face masks were used together with hand hygiene OR = 0.690 [0.568 - 0.838], p=0.0002). Overall between-study heterogeneity was large also in the subgroup analyses. ConclusionDespite the large between study heterogeneity, compliance bias and differences by environmental settings, the findings support the use of face masks to prevent respiratory infections. PROSPERO registration number CRD42020205523.