Immunization disparities in older Americans: determinants and future research needs.

BACKGROUND: Marked racial disparities persist in influenza and pneumococcal vaccinations among Medicare beneficiaries. This study sought to assess the contribution that patient, physician, health system, and area-level characteristics make to these racial disparities in immunization.
METHODS: Cross-sectional and decomposition analyses were performed on a nationally representative sample of 18,013 non-institutionalized Medicare beneficiaries who responded to the Medicare Current Beneficiary Survey (MCBS) in 2000 to 2002. The physician characteristics of interest included specialty type, accessibility, information-giving skills, perceived quality, and continuity of care. Health system characteristics included HMO enrollment and numbers of primary care physicians per elderly. The outcomes were receipt of influenza vaccine in the past year and ever having received a pneumococcal vaccine.
RESULTS: Immunization rates were below recommended levels for all Medicare beneficiaries. Disparities between white and black beneficiaries in the receipt of vaccinations were large-an absolute 17% difference for each vaccine. After adjusting for patient, physician, health system, and area-level characteristics, white beneficiaries had significantly higher odds of vaccination than did black beneficiaries: adjusted odds ratio (aOR) = 1.52 (95% confidence interval [CI] = 1.35-1.71) for influenza vaccination, and aOR = 1.82 (95% CI = 1.61-2.07) for pneumococcal vaccination. Beneficiaries with a usual physician that they rated as having good information-giving skills and whose practice was more accessible, had higher immunization rates. Beneficiaries with a primary care generalist as their usual physician had higher odds of immunization than those with a specialist as their usual physician. At the county level, a higher number of primary care physicians per elderly resident was associated with higher odds of immunization. Only 7% of the racial disparity in influenza immunization was explained by the measured characteristics of beneficiaries and their health systems.
CONCLUSIONS: Despite similar insurance coverage and presence of a usual physician, black beneficiaries were significantly less likely than their white counterparts to receive influenza and pneumococcal vaccinations. The implications for future research are discussed, including the need for system-based interventions that make the offering and discussion of vaccination routine.