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OpenTrials
Completed

NCT Number: NCT07132125

Conversations With AI Chatbots Increase Short-Term Vaccine Intentions But Do Not Outperform Standard Public Health Messaging

The goal of this clinical trial is to test whether short conversations with large language model (LLM) chatbots can persuade vaccine-hesitant parents to vaccinate their children against human papillomavirus (HPV). The study compares two chatbot styles to official public health information and to a no-message control. Parents of HPV-eligible children first complete a survey about their attitudes toward the HPV vaccine and their main concerns. They are then randomly assigned to read public health materials, have a three-minute conversation with either a default-style chatbot or a conversational-style chatbot tailored to their concern, or receive no message. The main outcome is change in intent to vaccinate immediately after the intervention, with follow-up surveys at 15 and 45 days.

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Key information

Conditions

HPV Vaccination Intent

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Participants are recruited online via Prolific

Philadelphia, Pennsylvania, 19104, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18 years and up
  • Living in Canada, the UK, or the USA
  • At least one child eligible for HPV vaccine based on country-specific guidelines who has not received any doses of the vaccine or whose vaccination status is unknown

Exclusion criteria

  • Failure to pass attention checks
  • Identified as non-human respondents by reCAPTCHA or other automated bot detection

Treatment and study plan

Default-style LLM chatbot

Behavioral

A large language model chatbot (GPT-4o) that delivers tailored persuasive messages to parents about HPV vaccination, using the model's default style with longer, structured responses. Participants engage in a three-minute, multi-turn conversation, with responses personalized to their top-rated vaccine concern identified in a pre-intervention survey.

Conversational-style LLM chatbot

Behavioral

A large language model chatbot (GPT-4o) that delivers tailored persuasive messages to parents about HPV vaccination in a conversational style, with short responses. Participants engage in a three-minute, multi-turn conversation, with responses personalized to their top-rated vaccine concern identified in a pre-intervention survey.

Public health informational materials

Behavioral

Official public health informational materials on HPV vaccination from the Centers for Disease Control and Prevention (U.S.), National Health Service (U.K.), or Public Health Agency of Canada, matched to the participant's country of residence. Materials are 589-680 words in length, cover HPV risks and benefits of vaccination, and are presented for three minutes before participants proceed.

Primary outcomes

  1. Change in intent to vaccinate child against HPV within the next 12 months

    Time frame: Baseline to immediately post-intervention

    Self-reported likelihood, on a 0-100 scale, of vaccinating the participant's youngest HPV vaccine-eligible child (identified in pre-survey) within the next 12 months. Measured before and immediately after the intervention to assess short-term changes in vaccination intent.

Secondary outcomes

  1. Change in intent to vaccinate child against HPV at 15-day follow-up

    Time frame: Baseline to 15 days post-intervention

    Self-reported likelihood, on a 0-100 scale, of vaccinating the participant's youngest HPV vaccine-eligible child within the next 12 months. Measured at baseline and 15 days after the intervention to assess durability of effects.

  2. Change in intent to vaccinate child against HPV at 45-day follow-up

    Time frame: Baseline to 45 days post-intervention

    Self-reported likelihood, on a 0-100 scale, of vaccinating the participant's youngest HPV vaccine-eligible child within the next 12 months. Measured at baseline and 45 days after the intervention to assess durability of effects.

  3. Change in general parental vaccine hesitancy (PACV-5)

    Time frame: Baseline to immediately post-intervention

    Change in scores on the 5-item Parent Attitudes about Childhood Vaccines (PACV-5) scale. Measured at baseline and immediately after the intervention.

  4. Change in intent to vaccinate child for influenza and COVID-19

    Time frame: Measured at baseline and immediately post-intervention.

    Self-reported likelihood, on a 0-100 scale, of vaccinating the participant's youngest eligible child for influenza or COVID-19 within the next 12 months.

  5. Change in importance ratings of HPV vaccine concerns

    Time frame: Baseline to immediately post-intervention

    Change in participant ratings (0-100 scale) of importance for each HPV vaccine concern (list derived from National Immunization Surveys) between baseline and immediately post-intervention.

  6. Clicks on HPV vaccine appointment scheduling link

    Time frame: Immediately post-intervention

    Whether participants click a provided link to schedule an HPV vaccine appointment through CVS during the post-intervention survey.

  7. Willingness to donate payment to vaccine education charity

    Time frame: Immediately post-intervention

    Percentage of survey payment participants choose to donate (0%, 10%, 30%, or 50%) to an immunization-related charity during the post-intervention survey.

  8. Willingness to be recontacted for future research

    Time frame: Immediately post-intervention

    Participant self-reported willingness (yes/no) to be contacted for future studies

  9. Ratings of empathy, usefulness, and relevance of intervention content

    Time frame: Immediately post-intervention

    Participant ratings (1-5 scale) of how empathetic, useful, and relevant they found the assigned chatbot conversation or public health reading material.

Sponsors and collaborators

Lead sponsor

University of Pennsylvania

Other

Registry information

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Aug 20, 2025
Registry last updated
Aug 20, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.