Changes in pneumococcal vaccination disparities by area-level social vulnerability during the COVID-19 pandemic among Medicare and Medicaid enrollees

Background

The COVID-19 pandemic amplified long-standing health disparities in the United States and spurred new research into factors associated with vaccine uptake. While much of the focus has been on COVID-19 vaccines, few studies have examined disparities in pneumococcal vaccination.

Methods

Using a retrospective cohort design, we assessed how disparities in county-level pneumococcal vaccination rates by social vulnerability level changed across two periods: before COVID-19 (Medicare: 2016–2019; Medicaid: 2017–2019) and during COVID-19 (2020−2022). Vaccination data were derived from the claims of adult Medicare enrollees (aged ≥65 years) and Medicaid enrollees (aged 19–64), whereas social vulnerability was measured using the Minority Health Social Vulnerability Index. We analyzed changes in vaccine uptake disparities using a difference-in-differences regression model adjusted for demographics and clinical factors.

Findings

Both before and during COVID-19, vaccination rates were lower among enrollees residing in high-vulnerability counties. During the pandemic, disparities in pneumococcal vaccination rates decreased among the 37.5 million Medicare enrollees analyzed but increased among the 8.1 million Medicaid enrollees. These patterns remained even after adjusting for enrollee demographic and clinical characteristics.

Interpretation

During COVID-19, Medicare enrollees exhibited reduced disparities in pneumococcal vaccination, possibly due to heightened risk perception, whereas Medicaid enrollees experienced widening gaps, likely driven by socioeconomic barriers. These findings highlight the complex interplay of individual demographic and clinical characteristics, and area-level social vulnerability in shaping vaccine uptake. To improve public health, initiatives should consider these multifaceted factors to effectively address disparities.