Objective: To estimate the cost-effectiveness and net medical care costs of programs for annual influenza vaccinations for the elderly in a health maintenance organization (HMO).
Design: Population-based, case–control study.
Setting: The Northwest Region of Kaiser Permanente, a prepaid group practice HMO in Portland, Oregon.
Participants: Kaiser Permanente members 65 years of age and older who had at least 1 month of HMO eligibility during any of nine influenza seasons in the 1980s.
Measurements: The HMO's costs for providing medical care and conducting vaccination programs were estimated using accounting data.
Results: 32% of high-risk elderly persons and 22% of non–high-risk elderly persons received influenza vaccinations. Aggregate vaccine effectiveness in preventing pneumonia and influenza hospitalizations was 30% (95% CI, 17% to 42%) for high-risk and 40% (CI, 1% to 64%) for non–high-risk elderly persons. The net savings to the HMO per vaccination was $6.11 for high-risk elderly persons and $1.10 for all elderly persons. The HMO incurred a net cost of $4.82 per vaccination for non–high-risk elderly persons.
Conclusions: Influenza vaccination rates in this HMO were relatively low for high-risk elderly persons. The medical care costs saved by preventing pneumonia and influenza through vaccination of high-risk elderly persons provide a compelling rationale to increase compliance with recommendations for annual influenza vaccination. Indirect benefits, such as prevention of suffering, incapacity, and lost wages, are likely to compensate for the small net cost of vaccinating non–high-risk elderly persons.