The Effectiveness of Postal Mail and Text Message-Based Childhood and Adolescent Immunization Recall in Minnesota.

Objectives: Evaluate the effectiveness and estimate the costs of postal mail and text message immunization recall methods.

Design: Randomized controlled trial.

Setting: Minnesota residents targeted for recall based on data from the Minnesota Immunization Information Connection.

Participants: Children (2-year-olds) and adolescents (13-year-olds) in Minnesota who are overdue for the routinely recommended vaccines in their respective age groups.

Intervention: Eligible individuals were randomized into 3 groups (postal mail, text message, control) and received up to 3 rounds of immunization recall throughout 2023.

Main outcome measures: Receipt of at least 1 of the study vaccines by the end of the program; being on track for all study vaccines by the end of the program.

Results: Adolescents receiving postal mail or text message recall were more likely to receive at least 1 study vaccine and be on track by the end of the intervention compared to the control group. In the childhood cohort, vaccine uptake was higher in the postal mail and text message groups after the first round of recall, but no differences between the 3 groups were observed after rounds 2 or 3. The postal mail group was 1.08 times more likely than those receiving text messages to be on track for both ages, although the total texting program costs were only 5.6% of the total postal mailing costs.

Conclusions: Immunization recall is effective in improving vaccine uptake, particularly for the HPV vaccine. Although there is some evidence suggesting that texting is slightly less effective than postal mail, the cost savings far outweigh this difference.