Accepted for/Published in: JMIR Public Health and Surveillance
Date Submitted: May 24, 2023
Date Accepted: Dec 22, 2023
Effects of Face Mask Mandates on COVID-19 Transmission in 51 Countries: Retrospective Event-Study
ABSTRACT
Background:
The question of the utility of face masks in preventing acute respiratory infections has received renewed attention in the context of the COVID-19 pandemic. However, given the inconclusive evidence of existing RCT, evidence based on real-world data with high external validity is missing.
Objective:
This study evaluated whether face mask mandates in 53 countries increased public face mask use and reduced weekly Sars-CoV-2 reproduction numbers and growth rates of COVID-19 cases and deaths.
Methods:
An event-study approach was applied to real-world data pooled from three different sources: country-level information on mask use was obtained from the COVID-19 Trends and Impact Survey. Data from the Oxford COVID-19 Government Response Tracker and the COVID-19 Our World in Data dataset provided information on face mask mandates and COVID-19 reproduction numbers and growth rates.
Results:
Mandates lead to an average increase in mask use by 8.54 percent points (95%-CI 2.65 to 14.44) and Sars-CoV-2 reproduction numbers declined on average by -0.35 units (95%-CI -0.56 to -0.14). While an effect of mask mandates was observed for weekly growth rates of COVID-19 cases (-6.40 percent points, 95%-CI -14.58 to 1.78), no changes in growth rates of COVID-19-related deaths (-0.22 percent points, 95% -6.84 to -6.39) were found. Our results are robust to alternate model specifications that control for additional containment policies, as well as counterfactual linear trends. Further, recommendations for voluntary mask use had no effect on mask use, reproduction numbers and growth rates. Conclusion: Mask mandates can be used as an effective measure to curb the spread of Sars-CoV-2. Our study adds external validity to existing RCTs on the effectiveness of face masks to reduce the spread of Sars-CoV-2.
Conclusions:
Mask mandates can be used as an effective measure to curb the spread of Sars-CoV-2. Our study adds external validity to existing RCTs on the effectiveness of face masks to reduce the spread of Sars-CoV-2.
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