Does Medicare managed care reduce racial/ethnic disparities in vaccination among the Medicare elderly during seasons with vaccine supply problems?

Research Objective: The literature reported that influenza vaccination rates were higher among Medicare managed care (MMC) plan enrollees than among Medicare fee-for-service (FFS) plan enrollees, and that Medicare MMC plans did not reduce persistent racial/ethnic disparities in influenza vaccination rates in this population. We tested whether MMC plans reduced such disparities relative to FFS plans during four influenza seasons with vaccine supply problems.

Methods: We conducted cross-sectional multivariate logistic regression analyses during four seasons with variable national vaccine supply: 2000-2001 (severe supply delay), 2001-2002 (moderate delay), 2003-2004 (moderate shortage) and 2004-2005 (severe shortage) seasons. We examined self-reported receipt of influenza vaccine among nationally-representative community dwelling non-Hispanic African American (AA), non-Hispanic White (W), and Hispanic (H) elderly aged 65 or older, enrolled in the Medicare Current Beneficiary Survey (MCBS), and enrolled in a Medicare FFS or MMC plan continuously from September through December in two consecutive seasons. Sample sizes of FFS/MMC were 1,971/446 and 2,025/351 for the 2000-2002 seasons and the 2003-2005 seasons, respectively. Because the enrollment in MMC or FFS was self-selected by beneficiaries, the inclusion of MMC enrollment as a covariate in a model could cause an endogeneity problem and bias all estimates in a model. Therefore, we conducted two separate models for FFS and MMC enrollees. Vaccination rates were estimated with adjustment for factors such as health status and socioeconomic characteristics.

Principal Findings: Our preliminary analyses showed mixed results regarding the effects of MMC plans in reducing racial/ethnic disparities. Based on unadjusted vaccination rates, racial/ethnic disparities in MMC plans (range: 11%-37%) were generally smaller than those in FFS plans (14%-30%), except in two cases: the W-H disparity in the 2000-2001 season and the W-AA disparity in the 2003-2004 season.

Using adjusted vaccination rates, racial/ethnic disparities in MMC plans (range: 4%-38%) were generally smaller than those in FFS plans (7%-22%) except three cases: the W-H disparity in the 2000-2001 and 2003-2004 seasons and the W-AA disparity in the 2003-2004 season. For these three cases, the difference between the two plans was 7.4%, 24.5% and 2.5%, respectively. In two out of these three cases, the vaccination rate among the respective racial/ethnic minority group was higher in FFS plans than in MMC plans, which is not consistent with the literature. All differences were statistically significant (p<.001).

Conclusion: There was no systematic difference in racial/ethnic disparities in influenza vaccination rates between Medicare FFS and MMC enrollees in the four influenza seasons examined.