To evaluate the effectiveness and cost of bidirectional short messaging service in increasing rates of vaccination and well child care (WCC) among adolescents.


We included all adolescents needing a recommended adolescent vaccine (n = 4587) whose parents had a cell-phone number in 5 private and 2 safety-net pediatric practices. Adolescents were randomized to intervention (n = 2228) or control (n = 2359). Parents in the intervention group received up to 3 personalized short messaging services with response options 1 (clinic will call to schedule), 2 (parent will call clinic), or STOP (no further short messaging service). Primary outcomes included completion of all needed services, WCC only, all needed vaccinations, any vaccination, and missed opportunity for vaccination.


Intervention patients were more likely to complete all needed services (risk ratio [RR] 1.31, 95% confidence interval [CI] 1.12–1.53), all needed vaccinations (RR 1.29, 95% CI 1.12–1.50), and any vaccination (RR 1.36, 95% CI 1.20–1.54). Seventy-five percent of control patients had a missed opportunity versus 69% of intervention (P = .002). There was not a significant difference for WCC visits. Responding that the clinic should call to schedule (“1”) was associated with the highest effect size for completion of all needed services (RR 1.89, 95% CI 1.41–2.54). Net cost ranged from $855 to $3394 per practice.


Bidirectional short messaging service to parents was effective at improving rates for all adolescent vaccinations and for all needed services, especially among parents who responded they desired a call from the practice.

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