Personalized Reminders for Immunization Using Short Messaging Systems to Improve Human Papillomavirus Vaccination Series Completion: Parallel-Group Randomized Trial

"SMS text message reminders could be used to increase the likelihood that caregivers will follow through with HPV vaccination series completion and could also be used to combat vaccination delay."

Research has demonstrated the effectiveness of mHealth short messaging service (SMS) text message interventions on vaccination coverage and timeliness. SMS text message reminders work as a call to action and help prompt caregivers who would otherwise vaccinate their children but may fail to bring their child back for vaccination. In the United States (US), completion rates among adolescents who initiate the human papillomavirus (HPV) vaccine 3-dose series are low. This US study compares the impact of precision (tailored educational) SMS text messages on HPV vaccine series completion with conventional SMS text message reminders in a pragmatic randomised trial.

The trial was conducted in 4 community health clinics in New York City, US, between December 2014 and December 2017. These clinics provide care for primarily publicly insured Latino patients who are generally members of a low-income, tightly knit, and highly connected community. Enrolled parents of adolescents aged 9-17 years who received the first HPV vaccine dose at 1 of the 4 clinics were randomised 1:1 to 1 of the 2 parallel, unblinded arms: precision SMS text messages (which included educational information, next dose due date, and site-specific walk-in hours) or conventional SMS text messages without educational information. Messages were sent in either English or Spanish, based on parent preferences.

The transtheoretical model of behaviour change guided the tailoring of the precision SMS text messages. This theory posits that individuals move through six stages of change: precontemplation, contemplation, preparation, action (in this case, vaccination), maintenance, and termination. For example, messages for parents in the precontemplation stage first notified them that their adolescents were in need of subsequent doses and why those doses were needed, whereas messages for parents in the contemplation stage provided information needed to answer any remaining questions they might have had regarding vaccination. (Some messages were responsive to user input, such that parents were able to self-tailor the content by texting back indicators for which items they wanted more information about.)

Overall, 12,000 messages were sent to the 956 parents who were enrolled in the study. The precision (475 families) and conventional (481 families) SMS text message arms had similarly high HPV vaccination series completion rates (344/475, 72.4% vs 364/481, 75.7%). Forty-two days after the first dose, two-thirds of families, not initially in the preparation stage, moved to preparation or vaccinated stage. Those in either SMS text message arm had significantly higher completion rates than nonenrollees (708/1503, 47.1% vs 679/1503, 45.17%; P<.001). Even after removing those needing only 2 HPV doses, adolescents receiving any SMS text messages had higher completion rates than historical controls (337/2823, 11.93% vs 981/2823, 34.75%; P<.001). A population-wide effect was seen from 2014 to 2016, above historical trends.

In short, the addition of educational information in SMS text messages targeted to the stage of caregiver vaccine decision-making did not provide additional benefits in this low-income, urban, minority population. However, those receiving SMS text message reminders had more timely series completion than historical controls and nonenrollees. SMS text messaging also led to population-level effects, illustrating the potential impact of such reminders. The very large differences in completion between enrollees and nonenrollees, as well as historical controls, are notable.

In explaining the findings, the researchers point to studies showing that prolonged exposure to similarly themed messages may lead to reactance or active resistance against the health behaviour the health message advocates. In addition, for parents with an unfavourable attitude toward vaccines, educational interventions have been found to reduce the intention to vaccinate. For the subset of the patient population in the present study who failed to interact with the SMS text messages, additional educational messages may have acted as a mental deterrent to bringing in their children for subsequent doses. It is possible that for certain populations, changing to a different modality is needed. Also, further research could be conducted to explore the benefit of this technology for direct youth use, as an increasing number of health interventions are geared toward adolescent self-use to encourage increases in their health autonomy.

According to the researchers, "SMS text message reminders function as an accessible, easy-to-use, low-cost remote intervention that can be rapidly deployed, although information detailing the economic impact and cost-effectiveness of these interventions should be evaluated in future studies."

In conclusion, although education information did not provide added benefit, "The results of this study, along with prior vaccine SMS text message reminder research, underscore the sustained role SMS text messaging can still play in providing a digital precision SMS text message health approach to behavioral interventions, even in the modern mobile use landscape."