RESUMEN

BackgroundDespite safe and effective vaccines to prevent Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infections and disease, a substantial minority of the US remains resistant to getting vaccinated. It is imperative to know if expanding vaccination rates could reduce community-wide Coronavirus 2019 (COVID-19) disease, not just among those vaccinated. MethodsNegative binomial models were used to estimate associations between U.S. county-level vaccination rates and county-wide COVID-19 incidence and mortality between April 23rd and September 30th, 2021. A two-week lag and a four-week lag were introduced to assess vaccination rate impact on incidence and mortality, respectively. Stratified analyses were performed for county vaccination rates 40%, and before and after Delta became the dominant variant. FindingsAmong 3,070 counties, each percentage increase in population vaccination rates reduced county-wide COVID-19 incidence by 0{middle dot}9% (relative risk (RR) 0. 9910 (95% CI: 0{middle dot}9869, 0{middle dot}9952)) and mortality by 1{middle dot}9% (RR 0{middle dot}9807 (95% CI: 0{middle dot}9745, 0{middle dot}9823)). Among counties with vaccination coverage >40%, each percentage increase in vaccination rates reduced COVID-19 disease by 1{middle dot}5%, RR 0{middle dot}9850 (95% CI: 0{middle dot}9793, 0{middle dot}9952) and mortality by 2{middle dot}7% (RR 0{middle dot}9727 (95% CI: 0{middle dot}9632, 0{middle dot}9823)). These associations were not observed among counties with <40% vaccination rates. Increasing vaccination rates from 40% to 80% would have reduced COVID-19 cases by 45{middle dot}4% (RR 0{middle dot}5458 (95% CI: 0{middle dot}4335, 0{middle dot}6873)) and deaths by 67{middle dot}0% (RR 0{middle dot}3305 (95% CI: 0{middle dot}2230, 0{middle dot}4898)). An estimated 5,989,952 COVID-19 cases could have been prevented and 127,596 lives saved had US population vaccination rates increased from 40% to 80%. InterpretationsIncreasing U.S. SARS-CoV-2 vaccination rates results in population-wide reductions in COVID-19 incidence and mortality. Furthermore, increasing vaccination rates above 40% has protective effects among non-vaccinated persons. Given ongoing vaccine hesitancy in the U.S., increasing vaccination rates could better protect the entire community and potentially reach herd immunity. FundingNational Cancer Institute