Mask Wearing and Control of SARS-CoV-2 Transmission in the United States

Rader, Benjamin; White, Laura F.; Burns, Michael R.; Chen, Jack; Brilliant, Joe; Cohen, Jon; Shaman, Jeffrey; Brilliant, Larry; Hawkins, Jared B.; Scarpino, Samuel V.; Astley, Christina M.; Brownstein, John S.

INTRODUCTION: Cloth face coverings and surgical masks have become commonplace across the United States in response to the SARS-CoV-2 epidemic. While evidence suggests masks help curb the spread of respiratory pathogens, research is limited. Face masks have quickly become a topic of public debate as government mandates have started requiring their use. Here we investigate the association between self-reported mask wearing, social distancing and community SARS-CoV-2 transmission in the United States, as well as the effect of statewide mandates on mask uptake. METHODS: Serial cross-sectional surveys were administered June 3 through July 27, 2020 via web platform. Surveys queried individuals’ likelihood to wear a face mask to the grocery store or with family and friends. Responses (N=378,207) were aggregated by week and state and combined with measures of the instantaneous reproductive number (R(t)), social distancing proxies, respondent demographics and other potential sources of confounding. We fit multivariate logistic regression models to estimate the association between mask wearing and community transmission control (R(t) <1) for each state and week. Multiple sensitivity analyses were considered to corroborate findings across mask wearing definitions, R(t) estimators and data sources. Additionally, mask wearing in 12 states was evaluated two weeks before and after statewide mandates. RESULTS: We find an upward trend in mask usage across the U.S., although uptake varies by geography and demographic groups. A multivariate logistic model controlling for social distancing and other variables found a 10% increase in mask wearing was associated with a 3.53 (95% CI: 2.03, 6.43) odds of transmission control (R(t) <1). We also find that communities with high mask wearing and social distancing have the highest predicted probability of a controlled epidemic. These positive associations were maintained across sensitivity analyses. Segmented regression analysis of mask wearing found no statistical change following mandates, however the positive trend of increased mask wearing over time was preserved. CONCLUSION: Widespread utilization of face masks combined with social distancing increases the odds of SARS-CoV-2 transmission control. Mask wearing rose separately from government mask mandates, suggesting supplemental public health interventions are needed to maximize mask adoption and disrupt the spread of SARS-CoV-2, especially as social distancing measures are relaxed.