Differential impacts of vaccine scandal by ethnic and socioeconomic factors: Evidence from China.

Widespread vaccination against important diseases plays a key role for global health security, particularly in the context of the COVID-19 pandemic. However, building and maintaining trust in immunization services remains challenging because of doubts about quality and safety of vaccines. China has periodically faced mounting pressure and even public outrage triggered by incidents of poor-quality vaccines. We aimed to evaluate the impact of the diphtheria, pertussis, and tetanus (DPT) vaccine scandal of 2018 in China and the ensuing misinformation on vaccination, and investigate differential responses to the scandal by ethnic and socioeconomic factors. With data from January 2017 to December 2018 in Sichuan province, China, we used a difference-in-differences (DID) method to compare the changes in the county-level monthly DPT vaccinations against the hepatitis B vaccinations, both before and after the DPT vaccine scandal. We found that the number of DPT vaccinations decreased by 14.0 percent in response to the vaccine scandal and ensuing misinformation. The number of vaccinations in minority regions, under-developed regions, and regions with poor medical resources decreased more than in non-minority regions, developed regions, and regions with good medical resources (24.5 versus 10.1 percent, 17.3 versus 8.3 percent, and 17.0 versus 8.7 percent, respectively). People did more online searching for "Substandard vaccine" and "DPT vaccine" after the scandal, with the socioeconomically advantaged group searching more compared with the socioeconomically disadvantaged group. The results suggest the urgent need to make true information about the vaccine easily accessible over the internet, especially for the socioeconomically disadvantaged groups. Our findings for China can also have implications for immunization service planning for better safeguarding public health in other countries, particularly developing ones.