Effectiveness of Adding a Mask Recommendation to Other Public Health Measures
Authors: Matthew A. Spinelli, David V. Glidden, Efstathios D. Gennatas, George W. Rutherford, Monica Gandhi
Journal: Annals of Internal Medicine (2021)

LettersAugust 2021Effectiveness of Adding a Mask Recommendation to Other Public Health MeasuresFREEMatthew A. Spinelli, MD, MAS, David V. Glidden, PhD, Efstathios D. Gennatas, PhD, George W. Rutherford, MD, Monica Gandhi, MD, MPHMatthew A. Spinelli, MD, MASUniversity of California, San Francisco, San Francisco, CaliforniaSearch for more papers by this author, David V. Glidden, PhDUniversity of California, San Francisco, San Francisco, CaliforniaSearch for more papers by this author, Efstathios D. Gennatas, PhDUniversity of California, San Francisco, San Francisco, CaliforniaSearch for more papers by this author, George W. Rutherford, MDUniversity of California, San Francisco, San Francisco, CaliforniaSearch for more papers by this author, Monica Gandhi, MD, MPHUniversity of California, San Francisco, San Francisco, CaliforniaSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L21-0397 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail TO THE EDITOR: We read with interest Bundgaard and colleagues' study (1) evaluating mask mandates in Denmark. We commend the authors for performing a randomized trial of a nonpharmaceutical intervention in the midst of the pandemic. Still, the study makes it difficult to draw conclusions about the effect of masks in preventing incident infection or severe COVID-19. Masks were provided and recommended to participants; however, masking was not commonplace in Denmark at the time, and 14% of participants reported experiencing social harms because of masking. Only 46% of participants reported wearing a mask as recommended. In addition, adherence was probably overreported, as has been seen in previous prevention studies for stigmatizing interventions (2). Of note, because of the complexity of interpreting self-reported adherence, HIV and sexually transmitted infection prevention trials are now designed to incorporate objective assessment of adherence.Bundgaard and colleagues' study would have benefitted from inclusion of implementation science principles, namely, understanding the desired behavior in its social context, cluster randomization, and assessment of intervention fidelity (3). We believe that recommending a potentially stigmatizing intervention in a few individuals within a community is a major flaw in a study designed to evaluate a policy intervention. Cluster randomization would have allowed an entire community to be randomly assigned to the recommendation, minimizing social harms to the participants and probably increasing adherence to the intervention. Assessment of intervention fidelity and acceptability through such measures as direct observation within the community would allow a more accurate interpretation of self-reported adherence data.Use of cluster randomization has other benefits. Masks are probably more effective in preventing forward transmission in the context of high community uptake and adherence. By randomly assigning isolated members in the community to the mask recommendation, this study design cannot answer whether a mask policy recommendation would be effective within a community (4). In addition, given the high proportion of asymptomatic COVID-19 infections, we do not know how many persons were infected within their household bubbles. An optimal design would pursue a cluster randomized approach with sufficient power to detect incident (with polymerase chain reaction testing) rather than prevalent (with serology) infections and assess disease severity by cataloging clinical outcomes (that is, evaluating whether masks lead to less severe infections because of reduced inoculum [5]).A mask recommendation for isolated members of a community is unlikely to be effective. We suggest that future studies assess the effect of recommendations to wear masks at the community level. This information will be more informative for public health officials trying to stem transmission and disease while awaiting an effective and widely available vaccine.References1. 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 Scholar2. Marrazzo JM, Ramjee G, Richardson BA, et al; VOICE Study Team. Tenofovir-based preexposure prophylaxis for HIV infection among African women. N Engl J Med. 2015;372:509-18. [PMID: 25651245] doi:10.1056/NEJMoa1402269 CrossrefMedlineGoogle Scholar3. Proctor EK, Powell BJ, McMillen JC. Implementation strategies: recommendations for specifying and reporting. Implement Sci. 2013;8:139. [PMID: 24289295] doi:10.1186/1748-5908-8-139 CrossrefMedlineGoogle Scholar4. Wenger DS, Triplette M, Crothers K, et al. Incidence, risk factors, and outcomes of idiopathic pneumonia syndrome after allogeneic hematopoietic cell transplantation. Biol Blood Marrow Transplant. 2020;26:413-20. [PMID: 31605819] doi:10.1016/j.bbmt.2019.09.034 CrossrefMedlineGoogle Scholar5. Spinelli MA, Glidden DV, Gennatas ED, et al. Importance of non-pharmaceutical interventions in lowering the viral inoculum to reduce susceptibility to infection by SARS-CoV-2 and potentially disease severity. Lancet Infect Dis. 2021. [PMID: 33631099] doi:10.1016/S1473-3099(20)30982-8 CrossrefMedlineGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: University of California, San Francisco, San Francisco, CaliforniaDisclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L21-0397. 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 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 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 ...