Health care systems are increasingly considering large language model (LLM)-based chatbots for vaccine communication, but evidence that they improve durable, behaviorally relevant outcomes beyond existing health materials is limited. This randomized clinical trial tested whether brief, multiturn LLM chatbot interactions increased parental intention to vaccinate children against human papillomavirus (HPV) compared with no intervention and government public health materials, and whether effects persisted. Parents in the US, Canada, and UK were recruited online from March 3 to May 25, 2025, with follow-up at 15 and 45 days. Eligible participants were adults with at least one HPV vaccine-eligible child who was unvaccinated or whose vaccination status was unknown. Participants were randomized to no-message control, country-matched government materials with at least 3 minutes of exposure, or a 3-minute GPT-4o chatbot interaction using either a default persuasive style or a shorter conversational style. The primary outcome was self-reported likelihood of vaccinating the child against HPV within 12 months, measured immediately after intervention on a 0-100 scale. Follow-up outcomes included vaccination intent and self-reported vaccination at 15 and 45 days. In total, 1297 participants were randomized (mean age 42.84 years; 72.1% female). Compared with no intervention, public health materials increased immediate vaccination intent (Cohen d = 0.53; 95% CI, 0.36-0.70), as did the default chatbot (d = 0.48; 95% CI, 0.30-0.65) and conversational chatbot (d = 0.33; 95% CI, 0.17-0.49). At 45 days, neither chatbot increased intent relative to controls, whereas public health materials maintained modest effects. No intervention increased self-reported vaccination uptake. Findings suggest well-designed public health materials may match or exceed short LLM chatbot conversations for HPV vaccine promotion.

翻译：医疗系统日益考虑使用基于大型语言模型（LLM）的聊天机器人进行疫苗沟通，但关于其能否在现有卫生材料基础上改善持久且行为相关的结局，证据尚不充分。本项随机临床试验旨在检验：与无干预措施及政府公共卫生材料相比，简短的多轮LLM聊天机器人互动能否提高父母为孩子接种人乳头瘤病毒（HPV）疫苗的意愿，以及该效果是否具有持续性。研究于2025年3月3日至5月25日在线招募美国、加拿大和英国的父母，并在第15天和第45天进行随访。符合条件的参与者为至少有一名符合HPV疫苗接种条件但未接种或接种状态不明的子女的成年人。参与者被随机分配至：无信息对照组、国家匹配的政府材料组（至少接触3分钟），或使用默认说服风格或简短对话风格的3分钟GPT-4o聊天机器人互动组。主要结局为干预后即刻测量的0-100分制自报12个月内为孩子接种HPV疫苗的可能性。随访结局包括第15天和第45天的接种意愿及自报疫苗接种情况。共1297名参与者接受随机分配（平均年龄42.84岁；72.1%为女性）。与无干预相比，公共卫生材料（Cohen d=0.53；95% CI，0.36-0.70）、默认风格聊天机器人（d=0.48；95% CI，0.30-0.65）及对话风格聊天机器人（d=0.33；95% CI，0.17-0.49）均即时提高了接种意愿。第45天时，两类聊天机器人的意愿提升效果与对照组无差异，而公共卫生材料仍维持适度效果。无任何干预措施提高了自报疫苗接种率。研究结果表明，精心设计的公共卫生材料在促进HPV疫苗方面可能不亚于甚至优于简短的LLM聊天机器人对话。