BACKGROUND: Routine immunizations for children aged 10 years and younger in the United States (US) currently cover 14 diseases. Updated estimates of public health impact are needed, given changes in disease epidemiology, evolving recommendations, and the dynamic nature of compliance with the immunization schedule.
METHODS: Pre-vaccine disease incidence was estimated before each routine vaccine was recommended, with average values across multiple years obtained directly from published literature or calculated based on disease surveillance data or annual case estimates from the published literature. Pre-vaccine incidence then was compared to current, post-vaccine incidence, which was generally calculated as average values over the most recent 5 years of available incidence data. Overall incidence estimates and estimates by age group were calculated. Differences in pre- and post-vaccine disease incidence rates were used to calculate the annual number of cases averted, based on 2019 US population estimates. This analysis did not separately estimate the proportion of disease incidence reduction that may be attributed to adult vaccines or booster doses.
RESULTS: Post-vaccine disease incidence decreased overall and for all age groups across all diseases evaluated. Decreases ranged from 17.4% for influenza to 100.0% for polio. Over 90% reduction in incidence was achieved for 10 of the 14 diseases evaluated (including reduction in incidence of rotavirus hospitalizations). Overall post-vaccine disease incidence estimates were highest for influenza, rotavirus, and varicella. Estimated annual cases averted by vaccination in 2019 ranged from 1,269 for tetanus to more than 4.2 million for varicella.
CONCLUSION: Routine childhood immunization in the US continues to result in high, sustained reduction in disease across all vaccines and for all age groups evaluated.
