COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

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Primary Prevention Nanda A, Hung I, Kwong A, et al. Efficacy of surgical masks or cloth masks in the prevention of viral transmission: Systematic review, meta-analysis, and proposal for future trial. J Evid Based Med. 2021 May;14(2):97-111. doi: 10.1111/jebm.12424. Epub 2021 Feb 9.

OBJECTIVE: Recommendations for widespread use of face mask, including suggested type, should reflect the current published evidence and concurrently be studied. This review evaluates the preclinical and clinical evidence on use of cloth and surgical face masks in SARS-CoV-2 transmission and proposes a trial to gather further evidence.

METHODS: PubMed, EMbase, and the Cochrane Library were searched. Studies of SARS-CoV-2 and face masks and randomized controlled trials (RCTs) of n = 50 for other respiratory illnesses were included.

RESULTS: Fourteen studies were included in this study. One preclinical and 1 observational cohort clinical study found significant benefit of masks in limiting SARS-CoV-2 transmission. Eleven RCTs in a meta-analysis studying other respiratory illnesses found no significant benefit of masks (±hand hygiene) for influenza-like-illness symptoms nor laboratory confirmed viruses. One RCT found a significant benefit of surgical masks compared with cloth masks.

CONCLUSION: There is limited available preclinical and clinical evidence for face mask benefit in SARS-CoV-2. RCT evidence for other respiratory viral illnesses shows no significant benefit of masks in limiting transmission but is of poor quality and not SARS-CoV-2 specific. There is an urgent need for evidence from randomized controlled trials to investigate the efficacy of surgical and cloth masks on transmission of SARS-CoV-2 and user reported outcomes such as comfort and compliance.

Discipline / Specialty Area Score
Public Health
Comments from MORE raters

Public Health rater

It's hard to imagine a more important topic currently. This systematic review found little evidence of benefit from masks, but nearly all the studies were of low or moderate quality, limiting the generalizability of the conclusions. I worry a bit about widely disseminating this due to the difficulty in presenting it in the media. Lack of evidence of benefit (as in this study) is very different from evidence of lack of benefit.