We examined the impact of voting on the spread of COVID-19 after the US primary elections held from March 17 to July 11, 2020 (1574 counties across 34 states). We estimated the average effect of treatment on the treated (ATT) using a non-parametric, generalized difference-in-difference estimator with a matching procedure for panel data. Separately, we estimated the time-varying reproduction number $R_t$ using a semi-mechanistic Bayesian hierarchical model at the state level. We found no evidence of a spike in COVID-19 deaths in the period immediately following the primaries. It is possible that elections can be held safely, without necessarily contributing to spreading the epidemic. Appropriate precautionary measures that enforce physical distancing and mask-wearing are likely needed during general elections, with larger turnout or colder weather.
No increase in COVID-19 mortality after the 2020 primary elections in the USA