Pay-It-Forward 23-Valent Pneumococcal Polysaccharide Vaccination Among Older Adults: Protocol for a Randomized Controlled Trial (Preprint)

<sec> <title>BACKGROUND</title> The 23-valent pneumococcal polysaccharide vaccine reduces the risk of pneumonia among adults by 38% to 46%. However, only a few older adults in resource-limited areas of China have received the pneumococcal vaccination. Pay-it-forward is a social innovation that offers participants free or subsidized health services and a community-engaged message, with an opportunity to donate to support subsequent recipients. </sec> <sec> <title>OBJECTIVE</title> This study aims to assess the effectiveness and cost-effectiveness of the pay-it-forward intervention in encouraging the uptake of the 23-valent pneumococcal polysaccharide vaccine in adults aged ≥60 years. </sec> <sec> <title>METHODS</title> A 2-arm, parallel randomized controlled trial will be conducted in 4 community health centers in Nanning city, Guangxi province, China. We will use a block randomization design. A total of 204 older adults will be randomly allocated in a 1:1 ratio to either the pay-it-forward group or the standard-of-care group. Each participant will complete a web-based questionnaire. The standard-of-care group will be required to pay for the vaccine themselves. In contrast, the pay-it-forward group will receive a 150 RMB (US $20.7) vaccination subsidy, postcards, and the opportunity to donate. The participants in both groups will be followed up in the second and fourth weeks after enrollment. The primary outcome will be uptake of the 23-valent pneumococcal polysaccharide vaccine, as determined by administrative data. Secondary outcomes include costs, pneumococcal vaccination knowledge, attitudes toward the vaccine, perceptions of gratitude, incidence of adverse reactions and adverse events, and the likelihood of recommending pneumococcal vaccination to others. </sec> <sec> <title>RESULTS</title> Participant recruitment and follow-up were conducted from January 2024 to September 2024. A total of 220 participants were enrolled. Finalized results are expected in June 2026. </sec> <sec> <title>CONCLUSIONS</title> This study will provide evidence on the effectiveness and economic costs of the pay-it-forward strategy for pneumonia vaccination among older adults. The findings could have implications for vaccination policy and offer a new approach for increasing vaccination in resource-limited areas. </sec> <sec> <title>CLINICALTRIAL</title> Chinese Clinical Trial Registry ChiCTR2400079410; https://www.chictr.org.cn/showprojEN.html?proj=213999 </sec> <sec> <title>INTERNATIONAL REGISTERED REPORT</title> DERR1-10.2196/70246 </sec>