Effectiveness of Adding a Mask Recommendation to Other Public Health Measures
Authors: Hans Gaines
Journal: Annals of Internal Medicine (2021)

LettersAugust 2021Effectiveness of Adding a Mask Recommendation to Other Public Health MeasuresFREEHans Gaines, MD, PhDHans Gaines, MD, PhDKarolinska Institute, Stockholm, SwedenSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L21-0398 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR: Bundgaard and colleagues' important large-scale study (1) investigated the benefit of wearing a mask to reduce the risk for COVID-19 during a daily average of 4.5 hours spent outside the home for 1 month. To truly evaluate the benefit of masks, investigators must eliminate the possible bias that the participants might instead have been infected during the 19.5 hours each day that they stayed at home.A total of 52 participants in the mask group and 39 control participants reported COVID-19 in their household. Of these, 2 participants in the mask group and 1 in the control group developed SARS-CoV-2 infection. However, more participants may have been exposed and infected by household members without reporting COVID-19 in their household if these household members had asymptomatic infection or only mild disease that was not suspected to be due to COVID-19. Both the mask and control groups may have included an equal number of misdiagnosed participants, infected through household contact but believed to be infected during time spent outside the home. The true difference between the groups—and thus the benefit of wearing a mask—should increase (albeit with wide CIs) if this bias had been controlled, because of the relatively low number of infections.The reported finding that only 3% of participants (3 of 95) were infected through household contacts during the study seems surprisingly low and supports a proposed risk for bias due to misdiagnosis.Reference1. Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, et al. Effectiveness of adding a mask recommendation to other public health measures to prevent SARS-CoV-2 infection in Danish mask wearers. A randomized controlled trial. Ann Intern Med. 2021;174:335-43. [PMID: 33205991]. doi:10.7326/M20-6817 LinkGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: Karolinska Institute, Stockholm, SwedenDisclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L21-0398. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoEffectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers Henning Bundgaard , Johan Skov Bundgaard , Daniel Emil Tadeusz Raaschou-Pedersen , Christian von Buchwald , Tobias Todsen , Jakob Boesgaard Norsk , Mia M. Pries-Heje , Christoffer Rasmus Vissing , Pernille B. Nielsen , Ulrik C. Winsløw , Kamille Fogh , Rasmus Hasselbalch , Jonas H. Kristensen , Anna Ringgaard , Mikkel Porsborg Andersen , Nicole Bakkegård Goecke , Ramona Trebbien , Kerstin Skovgaard , Thomas Benfield , Henrik Ullum , Christian Torp-Pedersen , and Kasper Iversen Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Carl Llor Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Janet Rand Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Henning Bundgaard , Anna K. Ringgaard , Daniel Emil Tadeusz Raaschou-Pedersen , Johan Skov Bundgaard , and Kasper K. Iversen Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Matthew A. Spinelli , David V. Glidden , Efstathios D. Gennatas , George W. Rutherford , and Monica Gandhi Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Brendan Moran Metrics August 2021Volume 174, Issue 8Page: 1193-1193 ePublished: 17 August 2021 Issue Published: August 2021 Copyright & PermissionsCopyright © 2021 by American College of Physicians. All Rights Reserved.PDF downloadLoading ...