Influenza Immunization: the Impact of Notifying Patients of High-risk Status

Background: The influenza immunization rate in the high-risk military and retired military population has not been reported. To determine this rate, and to test whether the rate could be improved by notifying patients of their high-risk status, a clinical trial was conducted using a postcard reminder as an intervention.

Methods: All 1068 high-risk patients enrolled in a large, residency-affiliated, military family practice department were identified. Of these, 519 patients were randomly selected to receive a reminder postcard; the remainder (549) were not sent a card. The immunization rates of each group were compared.

Results: A significantly higher percentage of those to whom postcards were sent received an influenza immunization (25.2% vs 9.1%, P less than .001). This difference was significant in all demographic groups except in those less than 21 years of age and those 21 to 40 years of age, in which very few patients presented for immunization. In those in the study group aged 65 years and over, 46.7% were immunized vs 20% of controls (P less than .001). Those aged 65 years and older and those in the higher income group had higher immunization rates, while those aged 40 years and under had very low immunization rates.

Conclusions: The influenza immunization rate among military beneficiaries in high-risk groups is low, but can be significantly improved with a reminder postcard. This intervention may be more effective in the older and higher-income segments of the high-risk population. The low immunization rates of the lower-income group and the younger age groups have significant public health implications and should be studied further.