Regional Disparities in the Uptake of Differentiated Influenza Vaccines

Abstract

Significant racial/ethnic inequities in the uptake of differentiated influenza vaccines (DIVs) have been previously reported, though less is known about regional disparities. We conducted a retrospective longitudinal study (2014/15-2017/18 influenza seasons) among privately insured adults aged 65+ years in the US. The exposure was beneficiary’s area of residence (US Census Bureau division) and outcome was type of influenza vaccine: differentiated (High-Dose [HDV], adjuvanted, recombinant, and cell-based) versus standard-dose egg-based. Among those vaccinated in physician offices, beneficiaries in the East North Central region were twice as likely to receive a DIV vs those in the South Atlantic, whereas those in the East and West South Central were least likely. Disparities became more pronounced in models adjusted for individual and community characteristics, suggesting that crude uptake estimates understate the true magnitude of disparities. Regional disparities remained even in fully adjusted models, pointing to currently poorly understood factors that may include quality of healthcare, client health literacy and engagement, and other political and cultural factors.