OBJECTIVES: To determine if an IVR intervention was associated with attainment of the preventive service of influenza immunization for older adults. METHODS: A MCO in the Eastern U.S. identified a cohort of members (n = 22,501) age 65 and over as of January 1st, 2002 who were eligible for influenza immunization based on the Health Plan Employer Data and Information Set (HEDIS) specifications. The intervention consisted of telephone calls with IVR system prompts to remind patients to get immunized. Rates of adherence were compared based on whether members received a reminder. Calls were classified as reminders if the targeted member was contacted directly, or called in to the system after having heard the reminder, or if the reminder was left with another household member or on an answering machine. Calls were classified as non-reminders if the member hung-up, no connection was made, or if the targeted member or another household member declined the intervention. The telephone intervention began October 10th, 2002 and ended January 21st, 2003. Claims data for immunizations were evaluated from October 10th, 2002 to March 31st, 2003. Multivariate logistic regressions evaluated associations between the intervention and odds of getting the influenza immunization, controlling for age group and gender. RESULTS: Of members receiving the IVR reminder 6.9% got influenza immunizations, while 3.2% of members not receiving the reminder got immunizations (p <0.0001). Logistic regression revealed significant associations between the IVR reminder and the likelihood of receiving the immunization, controlling for age group and gender (p <0.0001). Neither age group nor gender significantly affected the odds of getting an immunization. Members who received a reminder were 2.15 times (95% CI = 1.73 to 2.61) more likely to have an influenza immunization. CONCLUSIONS: Although influenza immunization rates remain low, IVR reminders produce higher rates of influenza immunizations and increase patient adherence in older adults.