Disparity between expected spatial accessibility and actual travel time to vaccination sites: Implications for COVID-19 immunization delays

The COVID-19 pandemic underscored the importance of equitable and timely vaccination access. This study examined the impact of discrepancies between actual and expected travel times to vaccination centers on the timeliness of full and booster COVID-19 vaccinations in Nueces County, Texas. Drawing on vaccination data from over 171,000 individuals aged 18 and older, we employed Cox proportional hazards models and survival analysis to explore how demographic characteristics, the Social Vulnerability Index (SVI), and geographic disparities influenced vaccination delays. Results revealed that longer-than-expected travel times significantly reduced the likelihood of timely vaccination (HR = 0.95 for full vaccination, HR = 0.89 for booster doses). Seniors demonstrated higher vaccination timeliness rates, but gaps persisted across gender, ethnicity, and race, with males and Hispanics experiencing greater delays. Interaction analysis highlighted compounded challenges for seniors and vulnerable populations when travel time discrepancies were larger. These findings emphasize the critical need for geographically targeted public health interventions to address socio-economic disparities and improve vaccine accessibility during health crises.