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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.
Bundgaard, Henning; Bundgaard, Johan Skov; Raaschou-Pedersen, Daniel Emil Tadeusz; von Buchwald, Christian; Todsen, Tobias; Norsk, Jakob Boesgaard; Pries-Heje, Mia M; Vissing, Christoffer Rasmus; Nielsen, Pernille B; Winsløw, Ulrik C; Fogh, Kamille; Hasselbalch, Rasmus; Kristensen, Jonas H; Ringgaard, Anna; Porsborg Andersen, Mikkel; Goecke, Nicole Bakkegård; Trebbien, Ramona; Skovgaard, Kerstin; Benfield, Thomas; Ullum, Henrik; Torp-Pedersen, Christian; Iversen, Kasper.
  • Bundgaard H; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Bundgaard JS; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Raaschou-Pedersen DET; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • von Buchwald C; Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (C.V., T.T., H.U.).
  • Todsen T; Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (C.V., T.T., H.U.).
  • Norsk JB; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
  • Pries-Heje MM; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Vissing CR; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Nielsen PB; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
  • Winsløw UC; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Fogh K; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
  • Hasselbalch R; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
  • Kristensen JH; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
  • Ringgaard A; The Heart Center, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (H.B., J.S.B., D.E.T., M.M.P., C.R.V., U.C.W., A.R.).
  • Porsborg Andersen M; Nordsjaellands Hospital, Hillerød, and Aalborg University Hospital, Aalborg, Denmark (M.P.A., C.T.).
  • Goecke NB; Centre for Diagnostics, Technical University of Denmark, Kongens Lyngby, Denmark (N.B.G.).
  • Trebbien R; National Influenza Center, Statens Serum Institut, Copenhagen, Denmark (R.T.).
  • Skovgaard K; Technical University of Denmark, Kongens Lyngby, Denmark (K.S.).
  • Benfield T; Center of Research & Disruption of Infectious Diseases, Amager and Hvidovre Hospital, Copenhagen University Hospital, Hvidovre, Denmark (T.B.).
  • Ullum H; Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark (C.V., T.T., H.U.).
  • Torp-Pedersen C; Nordsjaellands Hospital, Hillerød, and Aalborg University Hospital, Aalborg, Denmark (M.P.A., C.T.).
  • Iversen K; Herlev & Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark (J.B.N., P.B.N., K.F., R.H., J.H.K., K.I.).
Ann Intern Med ; 174(3): 335-343, 2021 03.
Article in English | MEDLINE | ID: covidwho-965786
ABSTRACT

BACKGROUND:

Observational evidence suggests that mask wearing mitigates transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is uncertain if this observed association arises through protection of uninfected wearers (protective effect), via reduced transmission from infected mask wearers (source control), or both.

OBJECTIVE:

To assess whether recommending surgical mask use outside the home reduces wearers' risk for SARS-CoV-2 infection in a setting where masks were uncommon and not among recommended public health measures.

DESIGN:

Randomized controlled trial (DANMASK-19 [Danish Study to Assess Face Masks for the Protection Against COVID-19 Infection]). (ClinicalTrials.gov NCT04337541).

SETTING:

Denmark, April and May 2020.

PARTICIPANTS:

Adults spending more than 3 hours per day outside the home without occupational mask use. INTERVENTION Encouragement to follow social distancing measures for coronavirus disease 2019, plus either no mask recommendation or a recommendation to wear a mask when outside the home among other persons together with a supply of 50 surgical masks and instructions for proper use. MEASUREMENTS The primary outcome was SARS-CoV-2 infection in the mask wearer at 1 month by antibody testing, polymerase chain reaction (PCR), or hospital diagnosis. The secondary outcome was PCR positivity for other respiratory viruses.

RESULTS:

A total of 3030 participants were randomly assigned to the recommendation to wear masks, and 2994 were assigned to control; 4862 completed the study. Infection with SARS-CoV-2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%). The between-group difference was -0.3 percentage point (95% CI, -1.2 to 0.4 percentage point; P = 0.38) (odds ratio, 0.82 [CI, 0.54 to 1.23]; P = 0.33). Multiple imputation accounting for loss to follow-up yielded similar results. Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.

LIMITATION:

Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others.

CONCLUSION:

The 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. The data were compatible with lesser degrees of self-protection. PRIMARY FUNDING SOURCE The Salling Foundations.
Subject(s)

Full text: Available Collection: International databases Database: MEDLINE Main subject: Pandemics / COVID-19 / Masks Type of study: Cohort study / Diagnostic study / Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Limits: Adult / Humans / Middle aged Country/Region as subject: Europa Language: English Journal: Ann Intern Med Year: 2021 Document Type: Article

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Pandemics / COVID-19 / Masks Type of study: Cohort study / Diagnostic study / Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Limits: Adult / Humans / Middle aged Country/Region as subject: Europa Language: English Journal: Ann Intern Med Year: 2021 Document Type: Article