Assessing the Impact of the 2018 Changchun Changsheng Vaccine Incident on Childhood Vaccination in China

"Information about how children's guardians reacted to this incident could be used to improve the information provided in future about childhood vaccination, and be used to decide how vaccination programs could respond following similar incidents."

China has experienced a series of serious vaccine incidents that have significantly undermined public confidence in vaccines. In the 2018 Changchun Changsheng vaccine incident, the vaccine manufacturer was accused of producing substandard diphtheria-tetanus-acellular-pertussis (DTaP) vaccines with compromised efficacy. Although no long-term sequelae or deaths were officially reported as a result of these substandard vaccines, claims that the substandard vaccines were poisonous spread widely on the internet and social media sites. This study aimed to estimate the impact of the vaccine incident on real-world vaccination behaviours in China.

A cross-sectional survey was conducted in 10 provinces in 2019. Vaccination records were collected from 5,294 children aged 6-59 months, with information on 75,579 vaccine doses for 7 National Immunization Program (NIP) vaccines and 2 non-NIP vaccines received from 2014 to 2019. Chi-square test, interrupted time series, and logistic regression were used to evaluate the impacts of vaccine incident on vaccination delay, measured as the proportion of delayed doses out of total doses in schedule.

The study found significant increases in doses delayed ≤3 months (19.12% to 22.51%, p = 0.000) and >3 months (7.17% to 11.82%, p = 0.000) for DTaP vaccine after the incident. By scaling nationally, there will be extra 2.1 million doses delayed ≤3 months and 2.8 million doses delayed >3 months in the year following this incident. Among all surveyed vaccines, the incident-involved DTaP vaccines experienced the biggest rise in the proportion of delayed doses (from 26% to 34%) following the vaccine incident, which was mainly driven by long-term vaccination delay. These findings indicate that the vaccine incident was negatively associated with timely vaccination, especially for the incident-involved DTaP vaccines.

More guardians choose expensive private-market substitutes containing DTaP elements over government-funded DTaP vaccines. Controlling for socio-demographic factors, doses scheduled after the incident have higher odds of delays for DTaP vaccine (odds ratio (OR): 3.49, 95% confidence interval (CI): 3.08-3.96) and other NIP vaccines (OR: 2.76, 95% CI: 2.55-2.99), but not for non-NIP vaccines. This shift in guardians' choice due to the vaccine incident revealed a public avoidance of incident-involved vaccines, despite imposing a large financial burden on the families involved. This burden may be mitigated by appropriate government action to ensure the safety of government-provided vaccines, the timeliness of vaccination service delivery, and the accurate communication of key information to the public.

The findings were consistent with research on other vaccine incidents worldwide using aggregated vaccination data. Rumours about the safety of oral polio vaccine (OPV) led to an 11-month boycott of OPV and a substantial decrease in its coverage, with only 13% of children aged 12-23 months fully vaccinated in Nigeria in 2003-2004, reaching the lowest point since 1998. This polio vaccine incident led to a resurgence of wild poliovirus transmission in Nigeria and other 20 previously polio-free countries by 2007. In China, after widespread media reports of infant deaths following HepB administration in December 2013, the use of HepB vaccines for newborns in 10 provinces decreased by 18.6%, from 53,653 doses the week before the incident to 43,688 doses during the week that HepB from the implicated company was suspended. Therefore, increases in vaccination delay following perceived safety signals that the present study found can challenge and disrupt ongoing vaccination programmes.

When vaccine incidents occur:

• The government should conduct thorough investigations and promptly implement measures to revise the vaccination plans. Following the 2018 Changchun Changsheng vaccine incident, revaccination was immediately scheduled for children who had received substandard DTaP vaccines, and the Chinese government passed the first Vaccine Administration Act, which aims to strengthen government supervision of the whole process.
• Transparent internal and external communication is crucial. Effective and precise communication of existing information by officials has the potential to foster public confidence, irrespective of the ongoing nature of the investigation. In addition, proactive measures should be taken to counteract the dissemination of misinformation.

In conclusion: "This study evaluated the changes in individuals' vaccination behavior, which might provide policy implications for potential vaccine incidents in the future..."