The mismatch between COVID-19 vaccination implementation and vulnerable population: Spatiotemporal analysis of neighborhood-level COVID-19 vaccination rates in San Diego, California

This study analyzed COVID-19 vaccination rates with socioeconomic factors in San Diego, using data from December 1, 2020, to June 30, 2022, at zip code level. We identify important social determinants of health for COVID vaccination implementation, including ages, ethnic groups, insurance and education level. Our findings revealed that neighborhoods with a higher proportion of older residents (age over 65) initially exhibited greater vaccination rates (r: 0.34), while areas with larger Hispanic populations experienced significantly lower early vaccination rates (r: −0.47). Early vaccination disparities persisted among Hispanic, African American, and less educated communities, as well as among the uninsured and less educated. Hotspot analysis and Moran's I analysis further indicated initial spatial distribution mismatches between vaccine distribution and confirmed case rates at the zip code level. Although elderly groups were prioritized in early rollout, outreach to other vulnerable groups remained limited. By later stages, targeted efforts—such as San Diego County's SAVE (Scheduling Assistance for Vaccine Equity) program—helped improve vaccine access in vulnerable ZIP codes. The study demonstrated the need for policy refinement to ensure equitable vaccine distribution across vulnerable demographics.