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Journal of Osteopathic Medicine


Context: With the rise of the Delta variant of SARS-CoV-2 and the low vaccination rates in the United States, mitigation strategies to reduce the spread of SARS-CoV-2 are essential for protecting the health of the general public and reducing strain on healthcare facilities. This study compares US counties with and without mask mandates and determines if the mandates are associated with reduced daily COVID-19 infection. US counties have debated whether masks effectively decrease COVID-19 cases, and political pressures have prevented some counties from passing mask mandates. This article investigates the utility of mask mandates in small US counties.

Objectives: This study aims to analyze the effectiveness of mask mandates in small US counties and places where the population density may not be as high as in larger urban counties and to determine the efficacy of countywide mask mandates in reducing daily COVID-19 infection.

Methods: The counties studied were those with populations between 40,000 and 105,000 in states that did not have statewide mask mandates. A total of 38 counties were utilized in the study, half with and half without mask mandates. Test counties were followed for 30 days after implementing their mask mandate, and daily new SARS-CoV-2 infection was recorded during this timeframe. The counties were in four randomly selected states that did not have statewide mask mandates. The controls utilized were from counties with similar populations to the test counties and were within the same state as the test county. Controls were followed for the same 30 days as their respective test county. Data were analyzed utilizing t-test and difference-in-difference analyses comparing counties with mask mandates and those without.

Results: These data showed statistically significant lower averages of SARS-CoV-2 daily infection in counties that passed mask mandates when compared with counties that did not. The difference-in-difference analysis revealed a 16.9% reduction in predicted COVID-19 cases at the end of 30 days.

Conclusions: These data support the effectiveness of mask mandates in reducing SARS-CoV-2 infection spread in small US counties where the population density may be less than in urban counties. Small US counties that are considering passing mask mandates for the population can utilize these data to justify their policy considerations.



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COVID-19, SARS-CoV-2, infection, mask mandate, pandemic, public health