Examining Long-Term Effects of Human Papillomavirus Vaccine Recommendation Messages: A 4-Month Follow-Up Survey of a Randomized Controlled Study in Japan.

We previously conducted a randomized controlled study to examine persuasive messages recommending HPV vaccination to mothers with daughters in Japan. That study showed that the three types of intervention message used (statistical information only, a patient's narrative in addition to statistical information, and a mother's narrative in addition to statistical information) all significantly improved mothers' intention to have their daughter(s) receive the HPV vaccine, in comparison with mothers who received no messaging. The present study is a follow-up survey to assess the long-term effect of the intervention. Four months after the initial study, in January 2018, participants in the previous study were contacted and queried about their current intention to have their daughter(s) receive the HPV vaccine. Statistical analysis was conducted using the paired t-test and analysis of variance. A total of 978 mothers participated in the current survey. Vaccination intention 4 months after intervention had decreased to a level that did not differ significantly from the level prior to intervention in all three intervention conditions. The amount of change in vaccination intention 4 months after intervention did not differ significantly among the three intervention groups (p = 0.871). A single exposure to messaging was insufficient to produce a persistent intervention effect.