Influenza vaccination in community elderly. A controlled trial of postcard reminders.

Available strategies to increase influenza vaccination rates in the elderly have not been tested in the private sector where most elderly receive care. We performed a randomized controlled trial of a postcard reminder in the three private general internal medicine practices. The observed vaccination rates of 55% in experimental patients (N = 262) and 54% in control patients (N = 278) were similar, though much higher than estimated national rates of 20%. The data indicated that the baseline (control group) vaccination rate was high probably because study participants were exposed to many community vaccination cues, separate from the study cue. That vaccination rates were not higher after additional exposure to the study cue suggests that a "ceiling effect" occurred. Including 70 patients not randomized into the trial because they received flu shots prior to randomization, the vaccination rate in patients who had a clinic visit during autumn months was 75% compared to a rate of 52% in patients not visiting the clinic (P less than .001). Our results suggest that vaccination rates can be considerably higher in the private sector than those reported in the past, and that both vaccination cues and direct patient contact appear important to promote vaccination. This and other studies suggest that traditional cues may have a ceiling effect, yielding vaccination rates no higher than 55 to 65%; further increases in rates will require other approaches.