Chatbot-Delivered Online Intervention to Promote Seasonal Influenza Vaccination During the COVID-19 Pandemic: A Randomized Clinical Trial

IMPORTANCE: Receiving seasonal influenza vaccination (SIV) is important for adults during the COVID-19 pandemic. There are few robust evaluations of tailored interventions for improving SIV uptake among adults 65 years or older. OBJECTIVE: To evaluate the relative efficacy of a stages of change (SOC)-tailored online intervention compared with a standard, non–SOC-tailored online intervention in increasing SIV uptake among Hong Kong residents 65 years or older. DESIGN, SETTING, AND PARTICIPANTS: This nonblinded parallel-group randomized clinical trial was conducted between December 1, 2021, and July 31, 2022, in Hong Kong, China. Eligible participants were 65 years or older, had Cantonese- and/or Mandarin-speaking skills, were community-dwelling, had Hong Kong residency, were smartphone users, and had not received SIV for the 2021 to 2022 influenza season. Participants were recruited through random telephone calls, and those who completed the baseline telephone survey were randomized to either the intervention or control group. Both complete case and intention-to-treat (ITT) analyses were performed. INTERVENTION: In the intervention group, a simplified rule-based chatbot first assessed participants’ SOC related to SIV uptake and then automatically selected and sent participants SOC-tailored online health promotion messages (videos) through a messaging application (WhatsApp; Meta) once every 2 weeks for 4 sessions. In the control group, the chatbot sent a link to access through the messaging application a standard online health promotion message (video) covering general SIV information every 2 weeks for 4 sessions. MAIN OUTCOMES AND MEASURES: The primary outcome was self-reported SIV uptake at month 6, which was validated by the research team. The secondary outcome was SOC measured at both baseline and month 6 by validated questions. RESULTS: A total of 396 participants (mean [SD] age of 70.2 [4.3] years; 249 females [62.9%]) were randomized to the intervention (n = 198) or control (n = 198) group. The ITT analysis showed that the validated SIV uptake rate was higher in the intervention group than the control group at month 6 (50.5% vs 35.3%; P = .002). The mean (SD) SOC score was higher in the intervention group than the control group (2.8 [1.4] vs 2.4 [1.4]; P = .02). More participants in the intervention group completed at least 1 episode of intervention than in the control group (77.3% vs 62.6%; P < .001). CONCLUSIONS: Results of this trial indicate that the SOC-tailored online intervention was more effective than the non–SOC-tailored intervention and may be a sustainable new method in increasing SIV uptake among adults 65 years or older. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05155241