Effectiveness of financial incentives on influenza vaccination among older adults in China: a randomized clinical trial

Objectives To investigate the short-term and long-term effectiveness of different level of financial incentives on increasing the willingness to vaccinate and vaccine uptake. Methods A randomized controlled trial was conducted to investigate the effectiveness of financial incentives of three groups with monetary incentives (CNY20, CNY40, and CNY60; 1 CNY=0.13EUR) vs a control group - CNY0- on influenza vaccine uptake among 720 older adults (≥60 years) in Beijing, China. The primary outcome was vaccine uptake, and the secondary outcomes were intention to vaccinate and length of time to immunization. Results Financial incentive significantly promoted higher intention to influenza vaccinate 120/178, 67.42% vs. 442/542, 81.55%; RR 1.21, 95%CI 1.02-1.42) and higher vaccination participation (74/178, 41.57% vs. 316/542, 58.30%; RR 1.39, 95%CI 1.10-1.75). CNY60 had the largest impact on the intention to vaccinate (15.00% vs. 13.48% and 13.90%) and vaccination uptake (19.42% vs. 14.05% and 16.67%) compared to CNY20 and CNY40. Time to vaccination was significantly lower among participants receiving incentives than those without ([37.21 days, 95%CI 34.33-39.99] vs. [48.27 days, 95%CI 43.47-53.07]; HR1.57, 95%CI 1.22-2.03). We found no long-term influence of financial incentives on vaccination decisions in the following year (217/542, 40.04% vs. 65/178, 36.52%; RR 1.08, 95%CI 0.82-1.42). Conclusions Our study suggests modest financial incentives will boost short-term influenza vaccination rates and shorten the length of time to immunization in China. No one single time financial incentive had a long-term effect on future vaccination behaviours or helped establish regular vaccination behaviours.