Shots, Shortages, and Structural Barriers: A County Level Study of U.S. Influenza Vaccination (2018-2023)

Abstract

The thesis examines the political, structural, and socioeconomic drivers of influenza vaccination disparities across U.S. counties from 2018 to 2023. Using a comprehensive county level panel dataset, this study employs fixed effects regressions to model how political partisanship, healthcare infrastructure, healthcare access, and socioeconomic variables shape vaccination rates among rural and urban counties. Key predictors include partisan voting margins, healthcare professional shortages, licensed pharmacist availability, and the density of Federally Qualified Health Centers and Rural Health Clinics. Results reveal that Republican leaning counties consistently show lower vaccination rates, while greater access to licensed pharmacists and Federally Qualified Health Centers are associated with higher uptake, especially in rural areas. Meanwhile the presences of Rural Health Centers had unintuitive negative association. This study further applies a two-stage least squares model to estimate the causal effect of vaccination on flu related morality, displaying a protective effect. The multidimensional nature of this study reveals the need for community based depoliticized and decentralized approaches to vaccine access and a reassessment of public infrastructure and trust in institutions.