Objective: To evaluate the impact of vaccine scale-up on population level covid-19 mortality and incidence in the United States.
Design: Observational study.
Setting: US county level case surveillance and vaccine administration data reported from 14 December 2020 to 18 December 2021.
Participants: Residents of 2558 counties from 48 US states.
Main outcome measures: The primary outcome was county covid-19 mortality rates (deaths/100 000 population/county week). The secondary outcome was incidence of covid-19 (cases/100 000 population/county week). Incidence rate ratios were used to compare rates across vaccination coverage levels. The impact of a 10% improvement in county vaccination coverage (defined as at least one dose of a covid-19 vaccine among adults ≥18 years of age) was estimated During the eras of alpha and delta variant predominance, the impact of very low (0-9%), low (10-39%), medium (40-69%), and high (≥70%) vaccination coverage levels was compared.
Results: In total, 30 643 878 cases of covid-19 and 439 682 deaths associated with covid-19 occurred over 132 791 county weeks. A 10% improvement in vaccination coverage was associated with an 8% (95% confidence interval 8% to 9%) reduction in mortality rates and a 7% (6% to 8%) reduction in incidence. Higher vaccination coverage levels were associated with reduced mortality and incidence rates during the eras of alpha and delta variant predominance.
Conclusions: Higher vaccination coverage was associated with lower rates of population level covid-19 mortality and incidence in the US.
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