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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