Vaccine
http://www.sciencedirect.com/science/journal/0264410X
Volume 30, Issue 36 pp. 5299-5448 (3 August 2012)

Regular Papers
Feasibility of a randomized controlled trial to evaluate Text Reminders for Immunization Compliance in Kids (TRICKs)
Original Research Article
Pages 5305-5309
Carolyn R. Ahlers-Schmidt, Amy K. Chesser, Tuan Nguyen, Jennifer Brannon, Traci A. Hart, Katherine S. Williams, Robert R. Wittler

Abstract
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.