Dugré N, Ton J, Perry D, Garrison S, Falk J, McCormack J, Moe S, Korownyk CS, Lindblad AJ, Kolber MR, Thomas B, Train A, Allan GM. Masks for prevention of viral respiratory infections among health care workers and the public: PEER umbrella systematic review. Can Fam Physician. 2020 Jul;66(7):509-517. PMID: 32675098; PMCID: PMC7365162.
Objective: To determine the effect of mask use on viral respiratory infection risk.
Data sources: MEDLINE and the Cochrane Library.
Study selection: Randomized controlled trials (RCTs) included in at least 1 published systematic review comparing the use of masks with a control group, either in community or health care settings, on the risk of viral respiratory infections.
Synthesis: In total, 11 systematic reviews were included and 18 RCTs of 26 444 participants were found, 12 in the community and 6 in health care workers. Included studies had limitations and were deemed at high risk of bias. Overall, the use of masks in the community did not reduce the risk of influenza, confirmed viral respiratory infection, influenzalike illness, or any clinical respiratory infection. However, in the 2 trials that most closely aligned with mask use in real-life community settings, there was a significant risk reduction in influenzalike illness (risk ratio [RR] = 0.83; 95% CI 0.69 to 0.99). The use of masks in households with a sick contact was not associated with a significant infection risk reduction in any analysis, no matter if masks were used by the sick individual, the healthy family members, or both. In health care workers, surgical masks were superior to cloth masks for preventing influenzalike illness (RR = 0.12; 95% CI 0.02 to 0.98), and N95 masks were likely superior to surgical masks for preventing influenzalike illness (RR = 0.78; 95% CI 0.61 to 1.00) and any clinical respiratory infections (RR = 0.95; 95% CI 0.90 to 1.00).
Conclusion: This systematic review found limited evidence that the use of masks might reduce the risk of viral respiratory infections. In the community setting, a possible reduced risk of influenzalike illness was found among mask users. In health care workers, the results show no difference between N95 masks and surgical masks on the risk of confirmed influenza or other confirmed viral respiratory infections, although possible benefits from N95 masks were found for preventing influenzalike illness or other clinical respiratory infections. Surgical masks might be superior to cloth masks but data are limited to 1 trial.
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Editor’s key points
- ▸ There is growing advocacy for the use of masks in the community to prevent transmission of viral respiratory infections. This systematic review found limited evidence that the use of masks might prevent viral respiratory infections.
- ▸ The use of masks by a group in the community setting appears to reduce influenzalike illness in those wearing masks. The pooled analysis showed a significant risk reduction (number needed to treat [NNT] = 24). Using masks within a family 1 to 3 days after someone has developed symptoms of a viral respiratory infection does not appear to prevent transmission to family members, no matter if the masks are used by the sick individual, the healthy family members, or both.
- ▸ Surgical masks are likely superior to cloth masks for preventing influenzalike illness in health care workers (NNT = 50) but the results are drawn from a single trial. N95 masks are likely superior to surgical masks for preventing influenzalike illness (NNT = 100) and clinical respiratory infections (NNT = 40) in health care workers.
