The primary objective of this study is to develop and evaluate a conversational AI service (chatbot) on social media platforms to obtain accurate and up-to-date vaccine information, and assess the impact of chatbot usage on users' vaccine confidence and acceptance in Hong Kong, Singapore, and Thailand.

The investigators will focus on vulnerable seniors and/or children from Hong Kong, Singapore and Thailand who have refused or delayed COVID-19 vaccination. Participants will be recruited by an online panel to meet the target quota by age and sex. Participants will then be randomly assigned to the intervention group and the control group. For both intervention and control groups, evaluation questionnaires will be given out to the study participants asking questions about their demographics, including age, sex, educational level, employment status and household income levels. Participants will then answer questions regarding COVID-19 vaccine confidence, including the effectiveness and safety of vaccines, and the motivations of the policymakers who decided on the needed vaccines. Participants will be asked about COVID-19 vaccine acceptance including the intention to receive COVID-19 vaccines, make plans to receive COVID-19 vaccines, and receive at least one dose of COVID-19 vaccines. The intervention group will then be asked to use the chatbot developed by the research team for up to two weeks. The chatbot is developed under the RE-AIM framework for formative, impact, and process evaluation of the intervention. The control group will have no exposure to the chatbot.

The chatbot will be supported with data from 1) social listening analytics for monitoring local real-time discourses in the digital space on COVID-19 vaccine hesitancy and misinformation, and 2) formative, baseline, and endpoint evaluation, which will generate evidence for development and improvement/refinement.

Inclusion Criteria:

• Hong Kong adult residents (English or Chinese users) with (a) unvaccinated senior parents/grandparents aged 60 (including those who received first dose after the announcement of the COVID passport on 4th of January) or (b) unvaccinated children aged below 18.
• Thailand adult residents (Thai users) with (a) unvaccinated senior parents/grandparents aged 60 or above or (b) unvaccinated children aged below 18.
• Singapore adult residents (English or Chinese users) with unvaccinated children aged between 5 to 11 years old.

Exclusion Criteria:

• People who do not meet the inclusion criteria.

Individual participant data that underlie the results reported in the article, after de-identification (text, tables, figures, and appendices), will be shared. A written data-sharing request for meta-analysis should be submitted by email with a methodologically sound proposal. Proposals should be directed to kathysleung@connect.hku.hk; to gain access, data requestors will need to sign a data access agreement.

Beginning 9 months and ending 36 months following article publication

Researchers who provide a methodologically sound proposal for meta-analysis. Proposals should be directed to Kathyleung@connect.hku.hk; to gain access, data requestors will need to sign a data access agreement.