Mailed reminders for area-wide influenza immunization: a randomized controlled trial

To determine if mailed reminders would increase area-wide influenza immunization for persons aged 65 and older.

A randomized, controlled trial.

Ten counties in Indiana.

Using a Medicare database, 10,000 subjects were selected randomly from 10 counties in Indiana and randomized for the study. Using pre-established criteria, 4503 persons in the control group and 4508 in the intervention group were eligible for study.

Intervention subjects received mailed reminders during the immunization season of 1995.

Data from mailed surveys, Medicare claims, and phone calls were used to determine immunization rates.

Of those surveyed who received immunization, only 63.4% filed a Medicare claim. Immunization rates were high in both groups but higher in the intervention group, 69.0% versus 64.2%. Age, presence of lung disease, assignment to the intervention group, presence of heart disease, and an age-sex interaction term were significantly and independently related to immunization.

The Healthy People Year 2000 goal (60% immunization for persons 65 and older) was exceeded in this population. Medicare claims data do not reflect immunization rates accurately. Mailed reminders, an inexpensive intervention, increased immunization rates area-wide and have potential for cost savings.