A Hybrid Chatbot to Promote Pneumococcal Vaccination Among Older Adults: A Randomized Clinical Trial.

Importance: There are few robust evaluations assessing the efficacy of chatbots to improve pneumococcal vaccination (PV) uptake among adults 65 years of age or older.

Objective: To evaluate the relative efficacy of a hybrid chatbot in increasing PV uptake among Hong Kong residents aged 65 years or older.

Design, setting, and participants: This partially masked, parallel-group randomized clinical trial was conducted between May 1, 2023, and November 30, 2024 in Hong Kong, China. Participants were aged 65 years or older, had a Hong Kong identity card, could speak and comprehend Cantonese, were smartphone and WhatsApp users, and had no prior PV uptake. Participants were recruited through random telephone calls and were randomized to either the stage of change group or the standard intervention group.

Interventions: In the stage of change group, the rule-based component of the hybrid chatbot assessed participants' stage of change regarding PV uptake and then delivered stage of change-tailored interventions at months 0, 1, 2, and 3. The natural language processing component of the hybrid chatbot provided real-time answers to participants' PV-related questions. In the standard intervention group, the chatbot sent participants a link to access a standard online video covering PV information at months 0, 1, 2, and 3.

Main outcomes and measures: The primary outcome was self-reported PV uptake at month 12, which was validated by the research team. The secondary outcome was participants' stage of change measured at month 0 and month 12 by using validated questions, with a score of 1 = precontemplation, 2 = contemplation, 3 = preparation, and 4 = action.

Results: A total of 374 participants (213 female [57.0%]; mean [SD] age, 69.6 [3.1] years) were randomized to either the stage of change group (n = 187) or the standard intervention group (n = 187). The intention-to-treat analysis showed that the validated PV uptake rate was higher in the stage of change group than in the standard intervention group (29.4% vs 18.7%; P = .01). The mean (SD) stage of change score was higher in the stage of change group than in the standard intervention group (2.2 [1.3] vs 1.9 [1.1]; P = .02). More participants in the stage of change group than in the standard intervention group completed at least 1 intervention session (79.7% vs 57.8%; P < .001).

Conclusions and relevance: In this randomized clinical trial, the hybrid chatbot was more efficacious than the standard intervention in increasing PV uptake among older adults in Hong Kong. A hybrid chatbot may be a sustainable PV promotion for older adults.

Trial registration: ClinicalTrials.gov Identifier: NCT05772117.