Wearing surgical masks in public spaces reduces risks of respiratory symptoms

1. Wearing surgical face masks was superior to not wearing surgical face masks in reducing the risk of respiratory symptoms over 14 days among Norwegian adults.

Evidence Rating Level: 2 (Good)

During the COVID-19 pandemic, wearing face masks was a widely implemented public health measure to limit the spread of the virus; however, its effectiveness in lowering the risk of respiratory infections is mixed. This pragmatic parallel two-arm individually randomized superiority trial thus evaluated the personal protective effect of wearing versus not wearing surgical face masks in public spaces over 14 days on self-reported symptoms consistent with a respiratory infection. This study was conducted in Norway between 10 February 2023 and 27 April 2023, after the most acute phase of the COVID-19 pandemic, but during the normal influenza season in the Nordic countries. 4647 adults > 18 years of age were randomised 1:1 to the intervention arm and control arm. 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. Participants in the control arm were assigned to not wear a surgical face mask in public places. Among the participants randomized, 4575 participants were included in the intention-to-treat analysis, with 2313 (50.6%) in the intervention arm (mean age ±SD = 51 ±15.2) years, female N (%) =1423 (61.5%)) and 2262 (49.4%) in the control arm (mean age ±SD = 51 ±16.3 years, female N (%) = 1365 (60.3%)). Number of participants that self-reported respiratory symptoms consistent with respiratory infection were 163 (8.9%) in the intervention arm and 239 (12.2%) in the control arm. Compared to not wearing a mask, wearing a mask reduced the odds and absolute risk of self-reported symptoms (marginal odds ratio (OR) 0.71, 95% CI 0.58 to 0.87; P = 0.001; absolute risk difference −3.2%, 95% CI −5.2% to −1.3%; P < 0.001). No statistically significant effect was found on self-reported or registered COVID-19 infection. Overall, study results suggest that wearing face masks may be effective in reducing the incidence of self-reported respiratory symptoms consistent with respiratory tract infections.

Click to read the study in BMJ

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