Relative Risk of COVID-19 Reinfection by Demographic and Vaccination Factors During the Period March 2020-October...

The risk of reinfection has been difficult to quantify throughout the pandemic, making the case for COVID-19 vaccination and receipt of booster doses to the public difficult for the public health community. To address this question, Michigan statewide COVID-19 infection and vaccination data was utilized in this cross-sectional study to determine the risk of reinfection by vaccination status. Cases were divided into subgroups by vaccination status, and the risk of reinfection in the various vaccination categories was then calculated by dividing the cumulative incidence of reinfection in a vaccine category by the cumulative incidence of reinfection of those not in that category Within this population, the risk of becoming reinfected was 1.6 times higher for those who were unvaccinated than those who were vaccinated; those with a primary series saw a 27% reduced risk of reinfections compared to those without a primary series. Those with an additional booster dose had a modest improvement, with 35% reduced risk of reinfection when compared to the other groups combined. These results provide population level data to support current public health vaccination recommendations.