Personalized AI Dialogues and Parents’ HPV Vaccine Intent: A Randomized Trial

BackgroundHPV vaccination rates in the United States remain substantially below the 80% target of Healthy People 2030. New approaches for increasing vaccination rates are needed. We tested whether brief text conversations with the artificial intelligence large language model (LLM) GPT-4 Turbo could significantly increase intentions to vaccinate children against HPV.MethodsWe conducted a pre-registered randomized clinical trial in which participants were assigned to a text conversation with GPT-4 Turbo in which the LLM (with no specific training) tried to persuade them to vaccinate against HPV, a CDC informational brochure, or a control conversation with the LLM about an unrelated topic. In October 2025, we recruited 7368 Americans via Cint Exchange who had unvaccinated eligible children or did not yet have children, and whose intentions to vaccinate their children against HPV was under 75 on a 0-100 scale. Participants completed pre- and post-intervention measures of HPV vaccination intentions for sons and daughters. Randomization was via Qualtrics, with no masking possible. Our primary outcome was change in HPV vaccination intentions.FindingsThe AI-dialogue significantly increased vaccination intentions relative to the control (sons: 9.73 points, 95% CI [6.89, 12.56], p < .001; daughters: 7.72 points, 95% CI [4.98, 10.46], p < .001); as did the brochure (sons: 8.04 points, 95% CI [4.83, 11.25], p < .001; daughters: 5.51 points, 95% CI [2.52, 8.50], p < .001). The differences between the AI-dialogue and the brochure were not statistically significant (sons, p = .268; daughters, p = .120). Post-assignment attrition rates did not significantly differ between treatment arms (AI-dialgue, 11.9pp; brochure, 14.2pp), although both arms had significantly more attrition than the control (5.1pp); our results were robust to baseline-carried-forward imputation. Post-hoc analysis found that the AI-dialogue was significantly more likely than the CDC brochure to produce large increases in vaccination intentions (e.g. >30 points). Fact-checking of all 15,559 AI-generated claims using an independent AI model with web search capability revealed high overall accuracy (median = 100/100, mean = 95.4/100 on a scale where 0 = completely inaccurate and 100 = completely accurate), with only 0.4% of claims being medically inaccurate.InterpretationDialogues with GPT-4 Turbo offer a potential strategy for increasing HPV vaccination intentions at scale.