COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

Quality Improvement, Primary Prevention Liang M, Gao L, Cheng C, et al. Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis. Travel Med Infect Dis. 2020 Jul - Aug;36:101751. doi: 10.1016/j.tmaid.2020.101751. Epub 2020 May 28.

BACKGROUND: Conflicting recommendations exist related to whether masks have a protective effect on the spread of respiratory viruses.

METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement was consulted to report this systematic review. Relevant articles were retrieved from PubMed, Web of Science, ScienceDirect, Cochrane Library, and Chinese National Knowledge Infrastructure (CNKI), VIP (Chinese) database.

RESULTS: A total of 21 studies met our inclusion criteria. Meta-analyses suggest that mask use provided a significant protective effect (OR = 0.35 and 95% CI = 0.24-0.51). Use of masks by healthcare workers (HCWs) and non-healthcare workers (Non-HCWs) can reduce the risk of respiratory virus infection by 80% (OR = 0.20, 95% CI = 0.11-0.37) and 47% (OR = 0.53, 95% CI = 0.36-0.79). The protective effect of wearing masks in Asia (OR = 0.31) appeared to be higher than that of Western countries (OR = 0.45). Masks had a protective effect against influenza viruses (OR = 0.55), SARS (OR = 0.26), and SARS-CoV-2 (OR = 0.04). In the subgroups based on different study designs, protective effects of wearing mask were significant in cluster randomized trials and observational studies.

CONCLUSIONS: This study adds additional evidence of the enhanced protective value of masks, we stress that the use masks serve as an adjunctive method regarding the COVID-19 outbreak.

Discipline / Specialty Area Score
Occupational and Environmental Health
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Hospital Doctor/Hospitalists
Internal Medicine
Public Health
Infectious Disease
Intensivist/Critical Care
Comments from MORE raters

Family Medicine (FM)/General Practice (GP) rater

A well-conducted meta-analysis documenting that wearing masks decreases the spread of respiratory viruses. If there are some who are following science and still question the utility of masks, then this meta-analysis has a purpose.

Intensivist/Critical Care rater

The significant level of heterogeneity of treatment effects that persists despite sub-group analysis is concerning. However this analysis strengthens the recommendation of universal mask use particularly in the setting of viral infections.

Public Health rater

This is a bad quality systematic review. It seems more like an ad for masks.

Respirology/Pulmonology rater

With the current state of affairs with COVID-19 infection, this is important research showing mask use in preventing the spread of respiratory viral infections. The funnel plot is clear in terms of mask use. This study is not specific to COVID-19, but does indicate general positive data regarding mask use.

Respirology/Pulmonology rater

Given the politicization of wearing masks, this evidence is vitally important to disseminate broadly and quickly, so that those who wish to be guided by science can respond accordingly.

Respirology/Pulmonology rater

This is a well-done meta-analysis that could very well inform policies on the use of masking in public, healthcare facilities, and in the home. This reviewer was impressed with the finding that surgical masks seem to provide more protection to the wearer than many have thought; that strategies to provide and improve masking in the homes of infected individuals is an untouched area that might be exploited to reduce infections even more.