The association of voter turnout with county-level coronavirus disease 2019 occurrence early in the pandemic

PURPOSE: The ongoing coronavirus disease 2019 (COVID-19) severely impacted both health and the economy. Absent an effective vaccine, preventive measures used, some of which are being relaxed, have included school closures, restriction of movement, and banning of large gatherings. Our goal was to estimate the association of voter turnout with county-level COVID-19 risks. METHODS: We used publicly available data on voter turnout in the March 10 primary in three states, COVID-19 confirmed cases by day and county, and county-level census data. We used zero-inflated negative binomial regression to estimate the association of voter turnout with COVID-19 incidence, adjusted for county-level population density and proportions: over age 65 years, female, Black, with college education, with high school education, poor, obese, and smokers. RESULTS: COVID-19 risk was associated with voter turnout, most strongly in Michigan during the week starting 3 days postelection (risk ratio, 1.24; 95% confidence interval, 1.16–1.33). For longer periods, the association was progressively weaker (risk ratio 0.98–1.03). CONCLUSIONS: Despite increased absentee-ballot voting in the primary, our results suggest an association of voter turnout in at least one state with a detectable increase in risks associated with and perhaps due to greater exposures related to the primary.