Researchers conducted a study to evaluate whether bidirectional short messaging service was a cost-effective way to increase rates of vaccination and well child care (WCC) among more than 4,500 adolescents. The study randomized 2,228 adolescents to the intervention and 2,359 to the control group. For the intervention group, parents received up to three personalized short messaging services with one of three response options: the clinic will call to schedule, the parent will call clinic, or stop the short messaging service. Results show that patients in the intervention group were more likely to complete all needed services, all needed vaccinations, and any vaccinations. A missed opportunity occurred in 75% of control patients, compared with 69% of intervention. The two groups did not have a significant difference for WCC visits. The net cost for the service was $855–$3,394 per practice. According to the researchers, the bidirectional short messaging service to parents effectively improved vaccination rates for adolescents, especially among parents who wanted a scheduling call from the practice.