MEDPAGE TODAY – Use of masks in both community settings and healthcare settings may slightly reduce risk of COVID-19, but the evidence base leaves much to be desired, the final installment of a living, rapid review of multiple studies found.
Roger Chou, MD, and Tracy Dana, MLS, both of Oregon Health & Science University in Portland, wrote in the Annals of Internal Medicine:
“The strength of evidence remained low for reduced risk for SARS-CoV-2 infection with surgical masks versus no mask on the basis of two prior randomized controlled trials and two observational studies and insufficient for N95 respirators versus no mask or cloth mask versus no mask.”
“There were no new studies and insufficient evidence for surgical versus cloth masks and N95 versus surgical masks.”
“Despite focusing on higher-quality studies, the evidence base continues to have important limitations. Randomized controlled trials (RCTs) were few and had some imprecision and methodological shortcomings.
“In addition, RCTs evaluated interventions to promote or encourage mask use and were designed pragmatically, improving applicability but potentially attenuating estimated effects due to suboptimal adherence and crossover.”
In all, three RCTs and 21 observational studies were included.
The authors were seeking answers to two questions:
- What is the effectiveness and comparative effectiveness of respirators (N95 or equivalent), face masks (surgical), and cloth masks in addition to standard precautions in community and healthcare (high- or non-high-risk) settings for prevention of SARS-CoV-2 infection?
- And what is the evidence for extended or reuse of N95 respirators for prevention of SARS-CoV-2 infection?
To get at the answer, they searched PubMed, MEDLINE, and Elsevier EMBASE for relevant studies; they also searched medRxiv and reviewed reference lists of relevant articles. Searches for the last update were done from June 2022 to January 2023.
Although they found no new studies of mask use versus non-use, one good-quality Danish RCT (n=6,024) found that a recommendation for mask use was associated with a small but statistically insignificant reduction in COVID risk …