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.