Summary
Among 4,575 Norwegian adults, those told to wear a surgical mask in public for 14 days reported respiratory symptoms less often (8.9% vs 12.2%; odds ratio 0.71, 95% confidence interval 0.58 to 0.87). Outcomes were self-reported symptoms, not confirmed infection.
Key points
- 8.9% of people asked to wear surgical masks in public reported symptoms of a respiratory infection, against 12.2% of those asked not to (odds ratio 0.71, 95% confidence interval 0.58 to 0.87).
- The absolute risk difference was 3.2 percentage points over 14 days.
- Outcomes were self-reported symptoms, and masks were assigned for public spaces only, not home or work.
- Design: pragmatic randomized trial in Norway, February to April 2023, with 4,575 adults analyzed; participants knew their group.
- Funding: Norwegian Institute of Public Health and Centre for Epidemic Interventions Research; some authors report WHO travel or contract support, and none report industry ties.