Objective: To assess the effectiveness of computer-generated telephone reminder and recall messages in increasing preschool immunization visits.
Design: Randomized, controlled trial.
Setting: Fourteen counties in urban and rural Georgia.
Study participants: Children (N = 8002) who were younger than 2 years; had telephone numbers listed in preexisting computerized immunization databases; and were due or late for immunization(s) during the 4-month enrollment period.
Intervention: Households of children were randomized to receive or not receive a general or vaccine-specific computer-generated telephone reminder or recall message the day before the child was due, or immediately after randomization if the child was late.
Main outcome measure: The rates of immunization visits during the 30-day follow-up period.
Results: Of the 4636 children whose households were randomized to receive a message, 1684 (36.3%) visited the health department within 30 days compared with 955 (28.4%) of the 3366 children whose households were not contacted (risk ratio [RR] = 1.28; 95% confidence interval [CI] = 1.20 to 1.37; P < .01). Immunization visits were more frequent (41.1%) among the 3257 children whose households actually received the message (RR = 1.45; 95% CI = 1.36 to 1.56; P < .01). Improvement in immunization visits was similar for general and specific messages, greater for recall than reminder messages, and greatest for children who were late for the third dose of the diphtheria-tetanus-pertussis vaccine and the measles-mumps-rubella vaccine.
Conclusion: These data suggest a simple and effective way to increase preschool immunization visits, particularly for vaccines associated with the lowest immunization rates.