Modelling a capacitated location problem for designing multimodal vaccine distribution network using a novel Health Emergency Susceptibility Index

Health emergency due to the outbreak of a contagious virus augments the need for effective vaccine distribution strategies to control its spread. This paper suggests a two-phase strategy to solve this problem. Phase I constructs a Health Emergency Susceptibility Index for each region, considering the disease data and comorbidity situation. Phase II uses the HESI and proposes three versions of priority weights for different application scenarios. These are used as the priority weights to formulate a capacitated location problem with a multimodal network and multiple types of refrigerators. The model considers additional factors like storage capacity, locations, transportation distances (including air and ground options), costs (maintenance and transportation), and vehicle capacity. To solve the model for large networks, the paper suggests a solution approach using Benders Decomposition with extreme directions. To validate the models, we examine the case of COVID-19 vaccine distribution in India. To assess the impact of the Susceptibility Index on facility locations, proposed weightage versions are compared with a version that does not use the index. The results show that one of the three versions with weighting schemes based on the population-to-susceptibility ratio leads to the most cost-effective distribution strategy, ensuring coverage of all susceptible regions. Furthermore, the Decomposition-based solution significantly improves computational efficiency, solving the problem over fifty times faster than the commercial solver.