Residual Disparities in US Adults Hospitalized due to All-Cause Pneumonia Following Implementation of Childhood 13-Valent Pneumococcal Conjugate Vaccine in National Immunization Program

This study investigated the long-term impact of the pediatric 13-valent pneumococcal conjugate vaccine (PCV13) program on the rates of inpatient all-cause pneumonia among US adults. Specifically, the researchers sought to determine if the observed reductions in disease burden were uniform across different demographic and socioeconomic groups, or if disparities persisted after the vaccine's implementation.

The researchers conducted a retrospective observational study using the Optum Clinformatics Data Mart Database, covering over 38 million US adults from 2007 to 2019. They stratified the population by age, race, comorbidity profile (low-risk vs. at-risk/high-risk), and household income. By comparing pneumonia hospitalization rates across four time periods—pre-PCV13, peri-PCV13, and two post-PCV13 intervals—the team calculated incidence rate ratios to assess changes in disease burden and identify ongoing health inequities.

The study found that inpatient all-cause pneumonia rates decreased across all age groups following the introduction of PCV13, with the most significant relative reductions (48%) occurring in adults aged 18–49. However, the magnitude of these reductions varied significantly by subgroup. By the final study period (2017–2019), Black adults, those with at-risk or high-risk medical conditions, and individuals with lower household incomes continued to experience a disproportionately higher burden of pneumonia compared to their counterparts. While the vaccine program successfully lowered overall disease rates, it did not eliminate these underlying socioeconomic and racial disparities.

These findings suggest that while universal pediatric vaccination provides substantial indirect (herd) protection for the broader population, it is insufficient to close the health equity gap for vulnerable adult populations. The persistence of these disparities highlights a critical need for targeted public health strategies, such as improved vaccine outreach and access, to address the specific needs of high-risk and lower-income groups who remain at elevated risk for severe pneumococcal disease.