Improving influenza vaccination rates by targeting individuals not seeking early seasonal vaccination

Influenza morbidity and mortality remain high in the United States although vaccination clearly improves health outcomes and reduces health expenditures. This study was designed to assess the effectiveness of mail and telephone reminder strategies on improving existing clinic influenza vaccination rates among those not seeking early seasonal vaccination.

In mid-November, we randomized 1371 patients at a hypertension clinic into 1 of 2 intervention groups, a mail reminder group (letter plus the Centers for Disease Control [CDC] Influenza Vaccine Information Statement) or a phone reminder group (same information via a personal phone call), or a control group. The following spring, records were reviewed for vaccination documentation. Patients without documentation were contacted by phone to identify whether vaccination for the current season had been obtained.

The final analysis included 884 patients (62% women, mean age 57.2 years old): 325 in the mail reminder group, 246 in the phone reminder group, and 313 represented the control group. Overall, 388 of these patients (44%) were vaccinated. Vaccination rates were significantly higher in the intervention groups, 46% for the mail reminder group (age and sex adjusted odds ratio [OR], 1.8, 95% confidence interval [CI], 1.3-2.5; P=.001) and 56% for the phone reminder group (OR, 2.8; 95% CI, 1.9-4.0; P<.0001), compared to 33% in the control group. Both interventions increased vaccination rates in all age/sex groups.

In contrast to earlier studies, this intervention occurred later in the influenza vaccination period excluding those who seek early vaccination and allowing interventions to target those less likely to receive vaccination. Compared to previous studies demonstrating only trivial or modest benefits, both mail and phone reminders effectively increased clinic vaccination rates in our group of patients.