SMS reminders increase on-time vaccination in Aboriginal and Torres Strait Islander infants.

Timely immunisation is important to protect children from communicable diseases. However, immunisation uptake in Aboriginal and Torres Strait Islander children under the age of two years is often lower than in non-Indigenous children. This contributes to the gap in health outcomes between Aboriginal and Torres Strait Islander children and non-Indigenous children. We have tested the effectiveness of short message service (SMS) reminders in improving timeliness of childhood immunisation in Aboriginal and Torres Strait Islander infants in regional Queensland, Australia. Reminders were sent to parents of Aboriginal and Torres Strait Islander children, at five immunisation age milestones: six weeks, four months, six months, 12 months, and 18 months. There was a significant improvement in the proportion of children vaccinated on-time (within 30 days of the due date), compared to an earlier age cohort, at all milestones except 12 months. The absolute risk difference (ARD) of on-time vaccination between the two cohorts ranged between 4.7% (95% confidence interval [95% CI]: 1.1-8.2%, at six weeks) and 12.9% (95% CI: 7.4-18.5%, at six months). The likelihood of on-time vaccination (rate ratio, RR) in the intervention group compared to the control group ranged from 1.05 (95% CI: 1.01-1.10, at six weeks) to 1.31 (95% CI: 1.14-1.50, at 18 months). SMS reminders were associated with an improvement in immunisation timeliness in Aboriginal and Torres Strait Islander infants at all age milestones measured except 12 months.