Does influenza vaccination of older adult Medicare beneficiaries lower treatment costs for acute and chronic respiratory disease?

ABSTRACT

BACKGROUND: Influenza accounts for a large proportion of hospitalizations and deaths among older adults, resulting in substantial health care expenses. Influenza vaccinations are effective in reducing respiratory infections in younger populations, but it is less certain whether they reduce costs associated with respiratory infections among older adults. OBJECTIVE: The purpose of this study was to determine whether influenza vaccination of older adult Medicare beneficiaries reduced costs associated with acute and chronic respiratory conditions during 3 recent influenza seasons. METHODS: This study analyzed the relationship between influenza vaccination and costs for respiratory conditions among Medicare beneficiaries >or=55 years of age in influenza seasons (October-May) between 2002 and 2005 using data from the Medicare Current Beneficiary Survey. Two-part multiple regressions of vaccination status were estimated on the probability and cost of treating respiratory conditions in each influenza season controlling for influenza risk factors and other covariates. Various sensitivity tests were conducted by type of service, subgroup analysis for specific population risk segments, propensity score-matched comparisons, and difference equations. RESULTS: The study sample included 13,402 Medicare beneficiaries for the 3 influenza seasons examined. Vaccination rates varied between 67.3% and 74.9% over the 3 influenza seasons. In unadjusted comparisons, no significant difference in the cost of treating respiratory conditions was found between vaccinated and unvaccinated beneficiaries in 2002/2003 (-$104), but vaccinated beneficiaries had significantly higher mean cost differentials in the more recent influenza seasons ($258 in 2003/2004, P = 0.012; $254 in 2004/2005, P = 0.003). Based on 2-part multiple regressions of vaccine status over the 3 seasons combined, costs of respiratory conditions were $142 dollars higher on average for vaccinated beneficiaries (P = 0.014). The base regression models showed no significant cost savings from vaccination in any year. Results of 2 of the 54 sensitivity tests that were conducted indicated significant savings from vaccination (inpatient costs for 2002/2003 and difference in total costs for persons unvaccinated in 2002/2003 but vaccinated in 2003/2004). CONCLUSION: In this study of older adults, no significant cost savings were found with influenza vaccines in the 3 influenza seasons examined (2002-2005) when the outcome was measured in terms of differential spending for acute and chronic respiratory conditions.