Cloth Masks May Prevent Transmission of COVID-19

Abstract

LettersApril 2021Cloth Masks May Prevent Transmission of COVID-19FREEKouji H. Harada, PhD, MPH, Mariko Harada Sassa, MD, PhDKouji H. Harada, PhD, MPHKyoto University Graduate School of Medicine, Kyoto, JapanSearch for more papers by this author, Mariko Harada Sassa, MD, PhDKyoto University Graduate School of Medicine, Kyoto, JapanSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L21-0088 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR: We appreciate Clase and colleagues' (1) efforts to show the potential efficacy of cloth masks in filtering virus-containing aerosols. The effect of wearing masks in the community to prevent coronavirus disease 2019 (COVID-19) is worth investigating. However, we have several concerns.Clase and colleagues cite an unpublished review (2) on the effects of face masks and state that integrated odds ratios were between 0.81 and 0.95. Three of the 4 cited odds ratios were derived in home environments where a member of the household was infected with influenza-like illness. Only 1 odds ratio integrated from 3 studies done in a university residence and during the hajj pilgrimage was 0.94 (95% CI, 0.75 to 1.19).Even if wearing masks reduces the risk for transmission by 6%, extrapolating how this measure will benefit the general community is difficult. Public health interventions requiring that populations wear masks may reduce transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) without harm. If authorities can spend sufficient funds, advocacy and distribution of materials are feasible. However, implementation of physical distancing, hand hygiene, and sanitation is not perfect. How should authorities allocate resources? The cost-effectiveness of cloth masks should be evaluated in comparison to that of other options.