Personal protective effect of wearing surgical face masks in public spaces on self-reported respiratory symptoms in adults: pragmatic randomised superiority trial
Runar Barstad Solberg, Atle Fretheim, Ingeborg Hess Elgersma, Mette Fagernes, Bjørn Gunnar Iversen, Lars G Hemkens, Christopher James Rose, Petter Elstrøm
BMJ, doi:10.1136/bmj-2023-078918
OBJECTIVE To evaluate the personal protective effects of wearing versus not wearing surgical face masks in public spaces on self-reported respiratory symptoms over a 14 day period.
DESIGN Pragmatic randomised superiority trial.
SETTING
Norway. PARTICIPANTS 4647 adults aged ≥18 years: 2371 were assigned to the intervention arm and 2276 to the control arm.
CONCLUSION Wearing a surgical face mask in public spaces over 14 days reduces the risk of self-reported symptoms consistent with a respiratory infection, compared with not wearing a surgical face mask.
AUTHOR AFFILIATIONS Contributors: All authors conceived and designed the study. RS is the guarantor. PE performed the statistical analysis. RS and IHE independently verified the data and statistical analyses. CR supervised the statistical analysis and reporting. RS wrote the first draft of the manuscript. AF, IHE, MF, BGI, LGH, CR, and PE critically reviewed and commented on each draft of the manuscript and approved the final manuscript for submission. RS, AF, IHE, MF, BGI, LGH, CR, and PE were responsible for the decision to submit the manuscript. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. LGH's institution (RC2NB) was contracted by WHO for the development of study protocol templates to evaluate public health and social measures; LGH received travel support from WHO; no other relationships or activities that could appear to have influenced the submitted work. Ethical approval: This study was approved by the Regional Ethics Committee South East Norway (reference 36544).
Data sharing: The final anonymised trial dataset and statistical codes will be freely available to the public through GitHub ( https://github. com/folkehelseinstituttet/2024-facemask-trial-bmj ). Transparency: The lead author (the manuscript's guarantor) affirms that the manuscript is an honest, accurate, and transparent account of
RESEARCH RESEARCH the study being reported; that no important aspects of the..
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"abstract": "<jats:title>Abstract</jats:title>\n <jats:sec>\n <jats:title>Objective</jats:title>\n <jats:p>To evaluate the personal protective effects of wearing versus not wearing surgical face masks in public spaces on self-reported respiratory symptoms over a 14 day period.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Design</jats:title>\n <jats:p>Pragmatic randomised superiority trial.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Setting</jats:title>\n <jats:p>Norway.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Participants</jats:title>\n <jats:p>4647 adults aged ≥18 years: 2371 were assigned to the intervention arm and 2276 to the control arm.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Interventions</jats:title>\n <jats:p>Participants in the intervention arm were assigned to wear a surgical face mask in public spaces (eg, shopping centres, streets, public transport) over a 14 day period (mask wearing at home or work was not mentioned). Participants in the control arm were assigned to not wear a surgical face mask in public places.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Main outcome measures</jats:title>\n <jats:p>The primary outcome was self-reported respiratory symptoms consistent with a respiratory infection. Secondary outcomes included self-reported and registered covid-19 infection and self-reported sick leave.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Results</jats:title>\n <jats:p>Between 10 February 2023 and 27 April 2023, 4647 participants were randomised of whom 4575 (2788 women (60.9%); mean age 51.0 (standard deviation 15.0) years) were included in the intention-to-treat analysis: 2313 (50.6%) in the intervention arm and 2262 (49.4%) in the control arm. 163 events (8.9%) of self-reported symptoms consistent with respiratory infection were reported in the intervention arm and 239 (12.2%) in the control arm. The marginal odds ratio was 0.71 (95% confidence interval (CI) 0.58 to 0.87; P=0.001) favouring the face mask intervention. The absolute risk difference was −3.2% (95% CI −5.2% to −1.3%; P<0.001). No statistically significant effect was found on self- reported (marginal odds ratio 1.07, 95% CI 0.58 to 1.98; P=0.82) or registered covid-19 infection (effect estimate and 95% CI not estimable owing to lack of events in the intervention arm). Self-reported sick leave was equally distributed between the intervention and control groups (marginal odds ratio 1.00, 0.81 to 1.22; P=0.97).</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Conclusion</jats:title>\n <jats:p>Wearing a surgical face mask in public spaces over 14 days reduces the risk of self-reported symptoms consistent with a respiratory infection, compared with not wearing a surgical face mask.</jats:p>\n </jats:sec>\n <jats:sec>\n <jats:title>Trial registration</jats:title>\n <jats:p>\n ClinicalTrials.gov\n <jats:ext-link xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"NCT05690516\" ext-link-type=\"clintrialgov\">NCT05690516</jats:ext-link>\n .\n </jats:p>\n </jats:sec>",
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