Effectiveness of Adding a Mask Recommendation to Other Public Health Measures
Authors: Henning Bundgaard, Anna K. Ringgaard, Daniel Emil Tadeusz Raaschou-Pedersen, Johan Skov Bundgaard, Kasper K. Iversen
Journal: Annals of Internal Medicine (2021)

LettersAugust 2021Effectiveness of Adding a Mask Recommendation to Other Public Health MeasuresFREEHenning Bundgaard, DMSc, Anna K. Ringgaard, PhD, Daniel Emil Tadeusz Raaschou-Pedersen, BSc, Johan Skov Bundgaard, BSc, Kasper K. Iversen, DMScHenning Bundgaard, DMScThe Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark, Anna K. Ringgaard, PhDThe Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark, Daniel Emil Tadeusz Raaschou-Pedersen, BScThe Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark, Johan Skov Bundgaard, BScThe Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark, Kasper K. Iversen, DMScHerlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, DenmarkAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L21-0401 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail IN RESPONSE: We thank readers for their many interesting comments and would like to address some of them here.We agree with Dr. Moran that the "lag" relating to infection late during the trial and time to seroconversion was to some extent captured by polymerase chain reaction assays. In our sample size calculation, we applied a power of 80% with an assumed infection rate of 2% in the control group. The power was ensured, because the infection rate was 2.1% in the control group and the number of participants who completed the study was slightly higher than the number needed to include according to the sample size calculation.We agree with Dr. Spinelli and colleagues that cluster randomization might be a good alternative to our randomization approach. However, in practical terms, performing such cluster randomization might be difficult. Will all or just most residents in the towns randomly assigned to wear masks accept doing so? What about those randomly assigned not to wear masks? Furthermore, because SARS-CoV-2 spreads in clusters, the number of randomized clusters should therefore be very large to ensure a nonbiased result. This would make such a study logistically difficult to implement.We instructed the participants in correct use of the masks, provided high-quality masks, delivered the masks to their homes free of charge, and assessed adherence through e-mail surveys 4 times during the study. The worst reported adherence was accounted for in analyses. We believe that adherence was very high—and most likely higher than what is seen during everyday use of face masks.Dr. Gaines may be correct that participants could have been infected at home from asymptomatic (that is, undiagnosed) members of their household. The participants were asked to wear masks only when outside the home, which is consistent with public health recommendations on use of masks. After all, it is difficult to imagine a recommendation to wear masks at home.We also agree with Dr. Llor that the circumstances have changed since April and May 2020 when we did our study. We do not believe that the cultural and social behavior in Denmark is so different from that of other countries. However, we do agree that such habits as kissing and hugging relatives, neighbors, and friends are different in different cultures and may represent a risk for SARS-CoV-2 transmission. We agree that the question of the effectiveness of masks in crowded places and when in proximity to others is important, and this was not addressed in our study. We tested the effect of adding mask wearing to the general recommendations, including the recommendation to keep a social distance of 1 to 2 m even in crowded places. However, we agree that more studies are needed to assess the efficacy of mask wearing in different settings.In response to Dr. Rand's comment, we would like to highlight that our study showed that "[t]he recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use" and that "[t]he findings, however, should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control of SARS-CoV-2 infection." Despite these statements in our article, some have misinterpreted our results and unfortunately made conclusions about questions that were not addressed by our study. Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, DenmarkHerlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, DenmarkDisclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M20-6817. 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 Hans Gaines 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 Carl Llor Effectiveness of Adding a Mask Recommendation to Other Public Health Measures Brendan Moran Metrics Cited byLessons Learned from In-Person Conferences in the Times of COVID-19 August 2021Volume 174, Issue 8Page: 1194-1195 ePublished: 17 August 2021 Issue Published: August 2021 Copyright & PermissionsCopyright © 2021 by American College of Physicians. All Rights Reserved.PDF downloadLoading ...