Feasibility of a Randomized Controlled Trial to Evaluate Text Reminders for Immunization Compliance in Kids (TRICKs)

Objective: To pilot test the Text Reminders for Immunization Compliance in Kids (TRICKs) program to evaluate its feasibility and potential to increase immunization coverage.

Design: Randomized controlled trial (RCT).

Setting: Pediatric clinic.

Participants: Parents of newborns being discharged from a local hospital who intended to seek child health care at the University-sponsored pediatric resident and faculty clinic.

Intervention: Text message immunization reminders prior to immunization due dates.

Main Outcome Measures: Receipt and timeliness of immunizations at 2, 4 and 6 months of age.

Results: Participants (N=90) were English (83%) or Spanish (17%) speaking. The majority were female (83%), on public insurance (59%), and had adequate health literacy (96%). Parents were married or a member of an unmarried couple (62%). Over 66% had a high school diploma or less. Greater numbers of intervention children received immunizations and were "on time" using per protocol analysis; though not statistically significance. Limitations include sample size, problematic text messaging software, and loss of phone service at 7 months for 40% of intervention parents. However, post-intervention interviews (N=18) indicated strong support for TRICKs; 83% found the text message reminders very helpful and 17% somewhat helpful.

Discussion: Pilot testing allowed us to assess processes, including recruitment, retention, and software, which will increase the success of an RCT. Software with built-in backup systems is needed for follow-up when mobile service is interrupted. However, in spite of limitations, immunization rates were higher in the text message reminder group, though not statistically significant. Parent support and interest was high. A fully powered RCT is needed with follow-up over the full 4-3-1-3-3-1 series. Based on our results, for 80% power where we expected 90% compliance in the intervention group and 80% in the control group we need 219 per group, plus increases to address drop out and loss of follow-up.