Introduction
INFLUENZA
Seasonal influenza vaccination (SIV) is effective in preventing influenza and all-cause mortality among individuals 65 years or older.There were a few randomized clinical trials (RCTs) comparing the mailing of simple and standard reminders vs no intervention; however, the effect size of these interventions was relatively small.The Transtheoretical Model (TTM)A chatbot is a computerized program that acts to replicate human interaction through text, speech, and visual forms of communication.This RCT was conducted to evaluate the relative efficacy of a SOC-tailored online intervention (the intervention group) compared with a standard, non–SOC-tailored online intervention (the control group) in increasing SIV uptake among Hong Kong residents 65 years or older. The online interventions in both groups were delivered by a simplified rule-based chatbot. We hypothesized that the intervention group would have higher absolute SIV uptake during the study period compared with the control group.