Optimizing vaccination sites for infectious diseases based on heterogeneous travel modes in multiple scenarios.

Equitable spatial accessibility to vaccination sites is essential for enhancing the effectiveness of infectious disease prevention and control. While traffic modes significantly influence the evaluation of spatial accessibility to vaccination sites, most existing studies measure it separately using homogeneous or single travel modes making it challenging to comprehensively understand the overall accessibility and support spatial optimization for vaccination sites. This study proposes to optimize the spatial distribution of vaccination sites based on heterogeneous travel modes in multiple scenarios by a hybrid travel time approach. This was done by first considering heterogeneous travel modes to measure spatial accessibility to vaccination sites followed by spatial optimization using hybrid travel time to determine the optimal configuration of vaccination sites across multiple scenarios. In the study area of Xiangtan, a prefecture-level city in east-central Hunan Province, China, spatial inequality in accessibility to COVID-19 vaccination sites were identified. The public in the Yuhu and Yuetang districts benefit from easy access to vaccination sites, and spatial accessibility within these areas is also equitable. By utilizing spatial optimization under the condition that the addition of a new site would not result in a comprehensive hybrid travel time increase exceeding 0.1%, up to 21 redundant sites were detected among the original ones and when newly added sites were considered, the optimal number of the optimized sites amounted to 124. These findings provide crucial spatial information to support for enhancing the efficiency of infectious disease prevention and control.