Public health impact of covid-19 vaccines in the US: observational study

Abstract

Abstract 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.