https://www.sciencedaily.com/releases/2021/04/210414154949.htm

During the COVID-19 pandemic, different states have enacted different policies on mask wearing, with some states having no mask requirements and others requiring masks in all public spaces. Understanding the link between mask wearing and COVID-19 rates could help inform policies to mitigate stress on healthcare systems, economic instability, and death.

To help clarify the effects of mask wearing, Fischer and colleagues examined publicly available data on mask-wearing policies, people's self-reported habits on mask wearing in public, and COVID-19 rates for all 50 U.S. states and Washington, D.C. They accounted for a one-month delay between mask wearing and its subsequent potential impact on COVID-19 rates from May through October 2020. For this analysis, they considered rates of more than 200 cases per 100,000 residents to be high.