Pay-it-forward 23-valent Pneumococcal Polysaccharide Vaccination Among Older Adults in China: A Two-arm Parallel Randomized Controlled Trial Protocol

Background: The 23-valent pneumococcal polysaccharide vaccine reduces the risk of adults developing pneumonia by 38-46%. However, only a small number of older adults in resource-limited parts of China have received 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 the next recipients. This trial aims to assess the effectiveness and cost-effectiveness of the pay-it-forward intervention in encouraging the uptake of 23-valent pneumococcal polysaccharide vaccine in adults aged 60 years and older. Methods: A two-arm parallel randomized controlled trial will be conducted in four community health centres in Nanning City, Guangxi Province, China. We will use a randomized block group 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 an online questionnaire. The standard-of-care group will be required to pay for the vaccine by themselves, whereas the pay-it-forward group will receive a 20.7 USD (150 RMB) vaccination subsidy, postcards, and the opportunity to donate. Participants in both groups will be followed up in the second and fourth week after enrollment. The primary outcome will be the uptake of 23-valent pneumococcal polysaccharide vaccine as determined by administrative data. Secondary outcomes include costs, pneumococcal vaccination knowledge, attitudes toward the vaccine, perceptions of gratitude, the incidence of adverse reactions and adverse events, and likelihood of recommending pneumococcal to others. Discussion: 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 strategy for increasing vaccination in resource-limited areas. Trial registration Chinese Clinical Trial Registry (ChiCTR), ChiCTR2400079410. Registered January 3, 2024.