During March 1–December 31, 2020, state-issued mask mandates applied in 2,313 (73.6%) of the 3,142 U.S. counties. Mask mandates were associated with a 0.5 percentage point decrease (p = 0.02) in daily COVID-19 case growth rates 1–20 days after implementation and decreases of 1.1, 1.5, 1.7, and 1.8 percentage points 21–40, 41–60, 61–80, and 81–100 days, respectively, after implementation (p<0.01 for all) (Table 1) (Figure). Mask mandates were associated with a 0.7 percentage point decrease (p = 0.03) in daily COVID-19 death growth rates 1–20 days after implementation and decreases of 1.0, 1.4, 1.6, and 1.9 percentage points 21–40, 41–60, 61–80, and 81–100 days, respectively, after implementation (p<0.01 for all). Daily case and death growth rates before implementation of mask mandates were not statistically different from the reference period.
Author(s): Gery P. Guy Jr., PhD1; Florence C. Lee, MPH1; Gregory Sunshine, JD1; Russell McCord, JD1; Mara Howard-Williams, JD2; Lyudmyla Kompaniyets, PhD1; Christopher Dunphy, PhD1; Maxim Gakh, JD3; Regen Weber1; Erin Sauber-Schatz, PhD1; John D. Omura, MD1; Greta M. Massetti, PhD1; CDC COVID-19 Response Team, Mitigation Policy Analysis Unit; CDC Public Health Law Program
Publication Date: 12 March 2021
Publication Site: CDC