AI Chatbot Use for Human Papillomavirus Vaccine Literacy in Japan: A Randomized Clinical Trial.

Importance: Persistent misinformation and low confidence impede human papillomavirus (HPV) vaccine uptake in Japan. Artificial intelligence (AI)-driven conversational agents may provide scalable vaccine education, but randomized evidence for HPV vaccine communication remains limited. Objective: To determine whether an AI-driven HPV vaccine chatbot improves caregiver HPV vaccine literacy compared with a government leaflet. Design, Setting, and Participants: Parallel-group randomized clinical trial (RCT) conducted through a national research panel of female caregivers in Japan with unvaccinated daughters aged 12 to 18 years from November 30 to December 27, 2024, with 2-week follow-up. Interventions: Participants were randomized 1:1 to an AI-driven HPV vaccine chatbot or standard government HPV vaccine leaflet. Main outcomes and measures: The primary outcome was an HPV vaccine literacy, evaluated immediately after intervention to estimate immediate intervention efficacy and evaluated at 2-week follow-up to estimate durability. HPV vaccine literacy was measured using 7 factual questions about HPV and HPV vaccination; scores are shown on a 0 to 7 scale, with higher scores indicating more correct responses.The secondary outcome was decision to vaccinate at 2-week follow-up. Results: Among 848 randomized participants, 704 of 841 (83.7%) were included in the immediate modified intention-to-treat (mITT) analysis (353 chatbot, 351 leaflet) and 477 of 841 (56.7%) in the mITT analysis at 2 weeks (237 chatbot, 240 leaflet). A total of 447 of 703 participants (63.6%) were aged 40 to 49 years and had college or university education (472 of 703 participants [67.1%]). Immediately after the intervention, analysis of covariance-adjusted literacy was higher with the chatbot (adjusted mean difference, 0.30 points on the 0 to 7 scale; 95% CI, 0.18-0.43 points; P < .001). At the 2-week durability assessment, mean (SD) literacy increased by 0.40 (1.21) with the chatbot vs 0.28 (1.13) points with the leaflet; adjusted literacy again favored the chatbot (adjusted mean difference, 0.30 points; 95% CI, 0.13-0.47; P < .001). At 2 weeks, caregivers' vaccination decisions did not differ between groups (102 of 253 participants [40.3%] vs 103 of 260 participants [39.6%]; adjusted odds ratio, 0.74; 95% CI, 0.41 to 1.33; P = .31). Conclusions and Relevance: In this RCT of female caregivers in Japan, an AI-driven HPV vaccine chatbot produced higher adjusted HPV vaccine literacy than a government leaflet immediately after intervention and at 2-week follow-up, without a measurable short-term effect on vaccination decision. Conversational AI may complement official materials and health care professional recommendations. Trial Registration: ClinicalTrials.gov Identifier: NCT06702423.