In the final update of a living, rapid review, authors conclude that “updated evidence suggests that masks may be associated with a small reduction in risk for SARS-CoV-2 infection in community settings. Surgical masks and N95 respirators may be associated with similar infection risk in routine patient care settings, but a beneficial effect of N95 respirators cannot be ruled out.”
The analysis is based on 3 randomized trials and 21 observational studies: “In community settings, mask use may be associated with a small reduced risk for SARS-CoV-2 infection versus no mask use, on the basis of 2 randomized trials and 7 observational studies. In routine patient care settings, surgical masks and N95 respirators may be associated with similar risk for SARS-CoV-2 infection, on the basis of 1 new randomized trial with some imprecision and 4 observational studies. Evidence from observational studies was insufficient to evaluate other mask comparisons due to methodological limitations and inconsistency.”
Editorial: “There is evidence that masks could work to prevent COVID-19, but substantial gaps remain about whether they do work and under what conditions,” editorialists write. “In the face of future viral outbreaks, we must move quickly to fill the gaps with timely studies that avoid the limitations of studies done to date. We may never reach definitive truth about when the benefit of masking interventions outweighs the harms, but it is imperative that we design studies that fill information gaps, interpret the evidence accurately, and are honest about what we do and do not know with certainty when making decisions and setting policy about masking.”