COVID-19 Vaccine Mandate and Vaccination Rates in the US Military, 2020‒2022

<b>Objectives.</b> To assess the effect of the vaccination mandate on COVID-19 vaccination rates and identify independent factors associated with lack of postmandate vaccination among service members. <b>Methods.</b> We assessed all active component service members for COVID-19 vaccination status from December 11, 2020, to January 1, 2022. We used comparative interrupted time series analysis and logistic regression to compare pre- and postmandate completion of the vaccine series between the US military and the US general population. <b>Results.</b> Previous documented infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), lower rank, and non-Hispanic Black race were associated with lower premandate vaccination. Postmandate vaccination rates were significantly higher in the active component population (<i>P</i> < .001) compared with the premandate period and the US population. Also notable was the higher incidence of postmandate vaccination among those who were non-Hispanic Black or of lower rank. <b>Conclusions.</b> The US military's COVID-19 vaccination mandate was effective at both increasing overall vaccination rates and reducing disparities in vaccination, including race and ethnicity and rank. Vaccine mandates increase the receipt of vaccines and promote health, readiness, and equity within the US military. (<i>Am J Public Health</i>. 2025;115(7):1146-1156. https://doi.org/10.2105/AJPH.2025.308120).