Pay-it-forward to improve influenza vaccine uptake and public engagement among children and older adults in China: A three-arm quasi-experimental study

Abstract China has low seasonal influenza vaccination rates among children and older adults. This quasi-experimental pragmatic trial examined the effectiveness of a pay-it-forward intervention on influenza vaccination compared to standard of care (user-paid vaccination) and free vaccination strategies among children and older people in China (ChiCTR2000040048). In pay-it-forward, people receive a free influenza vaccine from a local group and are offered an opportunity to donate financially to support vaccination among future individuals. The primary outcome was pre-specified as influenza vaccine uptake. Secondary outcomes included vaccine confidence and associated costs. Among 450 participants enrolled, 55/150 (36.7%) in the standard of care arm, 111/150 (74.0%) in the pay-it-forward arm, and 114/150 (76.0%) in the free vaccination arm received an influenza vaccine. The pay-it-forward arm had significantly higher vaccine confidence when compared to the standard of care arm. In the pay-it-forward arm, 107/111 (96.4%) of participants donated money for subsequent vaccinations and 19 of 60 invited (31.7%) created postcard messages.