tetano
Editor, Senior Moderator
Ann Intern Med
. 2020 Nov 18.
doi: 10.7326/M20-6817. Online ahead of print.
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
Henning Bundgaard[SUP] 1 [/SUP], Johan Skov Bundgaard[SUP] 1 [/SUP], Daniel Emil Tadeusz Raaschou-Pedersen[SUP] 1 [/SUP], Christian von Buchwald[SUP] 2 [/SUP], Tobias Todsen[SUP] 2 [/SUP], Jakob Boesgaard Norsk[SUP] 3 [/SUP], Mia M Pries-Heje[SUP] 1 [/SUP], Christoffer Rasmus Vissing[SUP] 1 [/SUP], Pernille B Nielsen[SUP] 3 [/SUP], Ulrik C Winsl?w[SUP] 1 [/SUP], Kamille Fogh[SUP] 3 [/SUP], Rasmus Hasselbalch[SUP] 3 [/SUP], Jonas H Kristensen[SUP] 3 [/SUP], Anna Ringgaard[SUP] 1 [/SUP], Mikkel Porsborg Andersen[SUP] 4 [/SUP], Nicole Bakkeg?rd Goecke[SUP] 5 [/SUP], Ramona Trebbien[SUP] 6 [/SUP], Kerstin Skovgaard[SUP] 7 [/SUP], Thomas Benfield[SUP] 8 [/SUP], Henrik Ullum[SUP] 2 [/SUP], Christian Torp-Pedersen[SUP] 4 [/SUP], Kasper Iversen[SUP] 3 [/SUP]
Affiliations
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.
. 2020 Nov 18.
doi: 10.7326/M20-6817. Online ahead of print.
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
Henning Bundgaard[SUP] 1 [/SUP], Johan Skov Bundgaard[SUP] 1 [/SUP], Daniel Emil Tadeusz Raaschou-Pedersen[SUP] 1 [/SUP], Christian von Buchwald[SUP] 2 [/SUP], Tobias Todsen[SUP] 2 [/SUP], Jakob Boesgaard Norsk[SUP] 3 [/SUP], Mia M Pries-Heje[SUP] 1 [/SUP], Christoffer Rasmus Vissing[SUP] 1 [/SUP], Pernille B Nielsen[SUP] 3 [/SUP], Ulrik C Winsl?w[SUP] 1 [/SUP], Kamille Fogh[SUP] 3 [/SUP], Rasmus Hasselbalch[SUP] 3 [/SUP], Jonas H Kristensen[SUP] 3 [/SUP], Anna Ringgaard[SUP] 1 [/SUP], Mikkel Porsborg Andersen[SUP] 4 [/SUP], Nicole Bakkeg?rd Goecke[SUP] 5 [/SUP], Ramona Trebbien[SUP] 6 [/SUP], Kerstin Skovgaard[SUP] 7 [/SUP], Thomas Benfield[SUP] 8 [/SUP], Henrik Ullum[SUP] 2 [/SUP], Christian Torp-Pedersen[SUP] 4 [/SUP], Kasper Iversen[SUP] 3 [/SUP]
Affiliations
- PMID: 33205991
- DOI: 10.7326/M20-6817
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.