Background To evaluate the feasibility and acceptability of a text message intervention to improve young people's knowledge of sexual reproductive health (SRH) and harms related to smoking in Indonesia.

A quasi-experimental short message service (SMS) trial of young people aged 16-24 years receiving twice weekly SMS over a 10-week intervention period. Pre- and post-online demographic and risk behaviour surveys were used to assess changes in knowledge. Among respondents who completed both surveys, we assessed changes in knowledge before and after SMS intervention using paired McNemar's test and differences in mean knowledge score using a paired t-test.

In total, 555 eligible young people were enrolled into the SMS intervention; 235 (42%) completed a follow-up survey, of which 198 (84%) were matched to a baseline survey. Median age of participants was 19 years and the majority were female (63%). The mean knowledge score significantly increased between baseline and follow-up surveys for SRH questions [2.7, (95% CI 2.47, 2.94) vs 3.4 (95% CI 2.99, 3.81) (P = <0.01)] and smoking-related questions [3.8 (95% CI 3.66, 3.99) vs 4.1 (95% CI 3.99, 4.28) (P = 0.03)]. A majority of participants reported that the SMS intervention increased their knowledge (95%) and were a useful reminder (95%).

An SMS intervention was feasible, acceptable and improved adolescents' SRH knowledge and smoking knowledge in a low- to middle-income setting. SMS interventions targeting young people need to be scaled up, with the potential to explore additional topics around healthy lifestyle, nutrition and physical activity.