Pay-it-forward to Increase the Uptake of Pneumococcal Vaccine among Older Adults: A Two-arm Randomized Controlled Trial in China

Background: Pneumococcal vaccination has a mortality benefit among older adults, but many do not receive it. This pilot study aims to evaluate the effectiveness of a pay-it-forward intervention on pneumococcal vaccine uptake among older adults in Guangxi Province, China. Methods: From January to September 2024, a two-arm parallel randomized controlled trial was conducted in four community health centers in Nanning City, Guangxi Province, China. We recruited older adults aged 60 or older who met the medical criteria for pneumococcal vaccine in the CHSCs. We used block randomization, and blocks of four older adults were assigned (1:1) to a pay-it-forward arm and a standard-of-care arm. The primary outcome was pneumococcal vaccination 1month after the intervention. Secondary outcomes included the influenza vaccination uptake, the cost-effectiveness of the pay-it-forward intervention, vaccine confidence, and peer vaccine referral. Results: 220 eligible older adults participated in the study, and 214 followed up at four weeks. Most participants were female (57.5%), 60-70 years old (59.3%), married (81.8%), had a high school education or less (73.8%), and had chronic diseases (69.6%). In the pay-it-forward arm, 70.2% (73/104) of participants received the PPSV-23 vaccine, and 31.7% (33/104) received the influenza vaccine, compared to 13.6% (15/110) and 17.3% (19/110), respectively, in the standard-of-care arm. Participants in the pay-it-forward group were more likely to receive the pneumococcal vaccine and influenza vaccine than those in the standard-of-care arm, with an adjusted odds ratio (aOR) of 19.4(95% CI: 8.88–46.6) and 2.43 (95% CI: 1.19-4.94), respectively. In addition, the participants in the pay-it-forward group exhibited higher confidence in vaccine safety (3.90, 95% CI: 1.63–10.33), vaccine administration (3.18, 95% CI: 1.00–11.97), vaccine importance (5.01, 95% CI: 2.01–14.08), and vaccine effectiveness (9.24, 95% CI: 2.98–36.84) than those in the standard-of-care group. 51.9%(54/104) participants contributed to donate for the next pay-it-forward recipients. The pay-it-forward group had a higher peer vaccine referral rate (41.4% vs. 58.6%, p=0.66) and had a lower economic cost per person vaccinated ($268.49 vs. $103.10) compared to the standard-of-care arm. Conclusion: These findings suggest that the pay-it-forward intervention Can increase pneumococcal and influenza vaccine uptake rates. This highlights the need for implementing pay-it-forward interventions and donation strategies to improve the uptake of necessary vaccinations. Trial registration: Chinese Clinical Trial Registry ChiCTR2400079410.