An HPV chatbot improved vaccine literacy without changing vaccination decisions
A randomized clinical trial in Japan found that an AI chatbot modestly improved HPV vaccine literacy compared with a standard government leaflet, but it did not measurably change caregivers' vaccination decisions after two weeks. The trial randomized 848 female caregivers of unvaccinated daughters aged 12 to 18. Its modified intention-to-treat analysis included 704 participants immediately and 477 at the two-week literacy follow-up. After adjustment, the chatbot group scored 0.30 points higher on a seven-point literacy scale at both time points. The decision result was different: 40.3 percent of assessed caregivers in the chatbot group and 39.6 percent in the leaflet group met the study's decision-to-vaccinate definition, with no statistically significant difference. The chatbot used GPT-4o with a Japan-specific library drawn from official and peer-reviewed material, stayed within a defined scope, and directed personal clinical questions to professionals. This is useful causal evidence for a narrow intervention, not proof that general-purpose chatbots improve health behavior. Attrition was substantial, participants were all female caregivers recruited online, most had college or university education, and follow-up was short. The clearest lesson is not that the chatbot failed. It is that knowledge and action are different outcomes. Scalable conversation may strengthen literacy, while trust, clinician relationships, access, and social context still determine what people do.