Effectiveness of a Pay-It-Forward Intervention Compared with User-Paid Vaccination to Improve Influenza Vaccine Uptake and Community Engagement among Children and Older Adults in China: A Quasi-Experimental Pragmatic Trial

"...contributes to the literature by assessing the effectiveness of a social innovation intervention using a quasi-experimental design, developing new methods for public influenza vaccination engagement, and enhancing vaccine uptake."

Low uptake of influenza vaccination in China can be traced to a lack of awareness, minimal community engagement, and limited public funding. In this context, the researchers performed a quasi-experimental pragmatic trial to examine the effectiveness of a pay-it-forward intervention (a free influenza vaccine and an opportunity to donate financially to support vaccination of other individuals) to increase influenza vaccine uptake compared with standard-of-care user-paid vaccination among children (aged between 6 months and 8 years) and older people (60 years and older) in China.

This study began with cocreation of the pay-it-forward intervention and engagement strategies with stakeholders (a Chinese vaccine expert, a communication specialist, a public health researcher, and a infectious disease physician with children) during a 3-day hackathon (November 4-6 2019), which is a sprint event that brings together diverse individuals to collectively solve a problem. The hackathon mapped out the following key components of the study: key stakeholders, potential user journeys, behavioural mechanisms, donation strategies, and engagement strategies. The latter included: inviting community members to co-design postcards; working in partnership with a local older adult to co-develop a video to explain pay-it-forward; inviting study participants to write postcard messages during recruitment for future participants; and engaging local medical staff. These key components were later contextualised into the local settings in China and iteratively adapted by involving local stakeholders and experts (i.e., community representatives, community-based vaccination clinic staff, pharmaceutical producers, a vaccine research expert, and communication specialists).

After a feasibility pilot study to inform the recruitment process and sample size calculations, the final step was the quasi-experimental pragmatic trial to evaluate the effectiveness of the intervention, which took place in three study sites: a rural site (Yangshan; lower income), a suburban site (Zengcheng; middle income), and an urban site (Tianhe; higher income). All three of the sites had fees associated with influenza vaccination for local residents.

Data collection began on September 21 2020 and ended on March 3 2021. Participants (n = 300) were introduced to the influenza vaccine by project staff using a pamphlet about influenza vaccination and were either asked to pay out-of-pocket at the standard market price (US$8.5-23.2; standard-of-care group) or to donate any amount anonymously (pay-it-forward group).

If participants in the pay-it-forward group decided to receive the vaccine, they were asked before vaccination whether they were willing to donate any amount of money into a pool of funds to support subsequent participants in receiving the same vaccine. They were assured that the donation was entirely voluntary, that any donation amount was acceptable, and that donation would not affect whether they received a vaccination or subsequent care. They were also invited to write anonymous postcard messages for future participants. The primary outcome was influenza vaccine uptake ascertained by administrative records. Secondary outcomes were self-reported vaccine confidence (defined as public trust in the vaccine safety, importance, and effectiveness) and cost of each strategy. Regression methods compared influenza vaccine uptake and vaccine confidence between the two groups.

Fifty-five (37%) of 150 people in the standard-of-care group (40 [53%] of 75 children and 15 [20%] of 75 older adults) and 111 (74%) of 150 in the pay-it-forward group (66 [88%] of 75 children and 45 [60%] of 75 older adults) received an influenza vaccine. People in the pay-it-forward group were more likely to receive an influenza vaccine compared with those in the standard-of-care group (adjusted odds ratio [aOR] 6·7 [95% confidence interval (CI) 2.7-16.6] among children and 5.0 [2.3-10.8] among older adults).

People in the pay-it-forward group had greater confidence in vaccine safety (aOR 2.2 [95% CI 1.2-3.9]), importance (3.1 [1.6-5.9]), and effectiveness (3.1 [1.7-5.7]).

Regarding participant contributions and engagement in the pay-it-forward group, 107 (96%) of 111 participants donated money for subsequent vaccinations, including those with a low annual income from a study site in the economically poor rural study site. The pay-it-forward group had a lower economic cost (calculated as the cost without subtraction of donations) per person vaccinated (US$45.60) than did the standard-of-care group (US$64.67).

Reflecting on the findings, the researchers suggest that the effect of pay-it-forward interventions might be related to the reduced costs of vaccination, enhanced community engagement, vaccine confidence, or a combination of these. Per the researchers, pay-it-forward interventions have social benefits, fostering community engagement, which "is central to the success of public health programmes....Engaging the community in vaccination services through cultivating kindness and reciprocity [e.g., through the writing of postcards] might also strengthen community solidarity and increase confidence in vaccine services..."

Full list of authors, with institutional affiliations: Dan Wu, Sichuan University, London School of Hygiene & Tropical Medicine (LSHTM), and University of North Carolina); Chenqi Jin, University of North Carolina, and Chinese Academy of Sciences; Khaoula Bessame, LSHTM; Fanny Fong-Yi Tang, LSHTM, University of North Carolina, and University of Hong Kong; Jason J Ong, LSHTM, Monash University, and Alfred Health; Zaisheng Wang, University of North Carolina, and University of Sheffield; Yewei Xie, University of North Carolina, and Duke University; Mark Jit, LSHTM; Heidi J Larson, LSHTM; Tracey Chantler, LSHTM; Leesa Lin, LSHTM, and Laboratory of Data Discovery for Health; Wenfeng Gong, Bill & Melinda Gates Foundation; Fan Yang, Peking University; Fengshi Jing, University of North Carolina, and Guangdong Secondary Provincial General Hospital; Shufang Wei, University of North Carolina; Weibin Cheng, Guangdong Secondary Provincial General Hospital; Yi Zhou, Zhuhai Center for Disease Control and Prevention, and Macau University of Science and Technology; Nina Ren, Guangdong Secondary Provincial General Hospital; Shuhao Qiu, Yangshan Health Centre; Jianmin Bao, Fenghuang Community Health Service Centre; Liufen Wen, Xinhua Community Health Service Centre; Qinlu Yang, Community Health Centre, Guangzhou; Junzhang Tian, Guangdong Secondary Provincial General Hospital; Weiming Tang, University of North Carolina, and Guangdong Secondary Provincial General Hospital; Joseph D Tucker, LSHTM, and University of North Carolina