Promoting Influenza Vaccination Uptake Among Chinese Older Adults Based on Information–Motivation–Behavioral Skills Model and Conditional Economic Incentive: Protocol for Randomized Controlled Trial

<b>Background</b>: Influenza poses a substantial health burden, especially among older adults in China. While vaccination is one of the most effective preventions, influenza vaccine uptake rates among Chinese older adults remain low. This study examines the individual and combined effects of behavioral interventions based on the Information-Motivation-Behavioral Skills (IMB) model and economic incentives in promoting influenza vaccine uptake among older adults living in China. <b>Methods</b>: The study will recruit 640 older adults living in eight communities that have not been covered by the free influenza vaccination policy. These eight communities (as clusters), stratified by urban and rural, will be randomized to four parallel arms, including a usual care arm, an IMB-based behavioral intervention arm, a conditional economic incentive arm, and a combined behavioral-economic arm. The interventions will start from the beginning of the flu season and last for about one month. Specifically, the IMB-based behavioral intervention encompasses health education brochures, healthcare provider-led lectures, interactive quizzes, and personalized consultations. The exact number of economic incentives is conditional on the timing of vaccination (a higher amount for early immunization) and the number of people within a household to be vaccinated at the same appointment (a higher amount for more people). The primary outcome is the influenza vaccination rate. Data will be gathered through vaccination records and questionnaires covering IMB-based vaccination cognitions. Mixed-effects models will be used to analyze the outcome of vaccination rate, reporting difference-in-differences estimates with 95% confidence intervals. <b>Conclusions</b>: The results of this study have the potential to inform influenza vaccination program scaleup among older adults who are not yet covered by the free influenza vaccination policy. <b>Ethics and dissemination</b>: Ethics approval has been granted by the ethics commission of Peking University Health Science Centre (IRB00001052-24090). Participants will be required to sign a written consent form. Findings will be reported in conferences and peer-reviewed publications in accordance with the recommendations of the Consolidated Standards of Reporting Trials. <b>Registration number</b>: This study was registered at the Chinese Clinical Trial Registry (ChiCTR2400090229).