Optimal COVID-19 Vaccination Facility Location
39 Pages Posted: 15 Jan 2022
Date Written: January 14, 2022
Problem Definition: Socioeconomic disparities in COVID-19 vaccination rates are partially attributable to poor vaccination site selection, often requiring excessively burdensome travel distances among some communities. In early 2021, the U.S. federal government launched partnerships with several retail pharmacy chains to provide additional vaccine access points, yet these locations are inefficiently selected. We consider an optimal facility location problem with existing retail pharmacy stores and proposed dollar stores as candidate vaccination locations as a mechanism to mitigate travel distance disparities across demographic groups.
Methodology/Results: We formulate this problem as a large-scale mixed-integer program with an objective of minimizing average travel distance to a vaccination site while covering all demand. Assigning each census tract to a vaccination site(s), we measure the resulting travel distance by jurisdiction and demographic group. Results indicate that replacing some of the 58,000 existing vaccination sites with optimally selected dollar stores could reduce average travel distances nationwide by 62%, with several states (Nebraska, Kansas, Missouri, Illinois and South Dakota) improving by 80% or more. Using a newly constructed distance Gini coefficient, we find substantial reductions in travel disparities by racial group, with the largest gains in Illinois, Tennessee, Nevada and Texas. Varying the number of potential stores and vaccination-capacity per store suggests that selecting where to strategically locate is more critical than altering the quantity or capacity of stores. Using cross-sectional and panel vaccination data for California---and exploiting variation in the opening and closures of mass vaccination sites---we document empirical evidence of a strong negative relationship between travel distance to a vaccination site and vaccination uptake.
Managerial Implications: Our study offers an interpretable, quantitative framework that can help federal and state health departments with future vaccination site selection to improve booster vaccine access, particularly for marginalized populations.
Keywords: COVID-19, Vaccine access, Facility location, Equity, Mixed-integer programming
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