Assessing vaccine effectiveness for varicella in Wuxi, China: a time-series analysis

OBJECTIVE: The varicella vaccine is not included in the national childhood immunization schedules in China. Varicella epidemics and outbreaks are frequently reported, and the evidence for the effectiveness of the varicella vaccine remains unclear. The aim of this study was to investigate varicella vaccine effectiveness in Wuxi, China. METHODS: Varicella surveillance data were extracted from the China Information System for Disease Control and Prevention, and vaccination data were obtained from the Vaccination Integrated Service Management Information System of Jiangsu Province, China. Time-series analysis approaches were used to estimate varicella vaccine effectiveness. RESULTS: A total of 16,093 varicella cases among children aged 1–6 years between January 2016 and December 2020 were analysed. A total of 217,297 children completed a two-dose varicella vaccination series. Compared with districts with lower vaccination rates, districts in Wuxi with higher varicella vaccination rates had a lower proportion of cases (p < 0.001). In the time-series approach, 0.8% fewer varicella cases were associated with a 1% increase in the two-dose varicella vaccination rate (p < 0.001), and similar effects were found in both the male and female populations. CONCLUSIONS: Two-dose varicella vaccination was recommended as an effective health intervention to prevent varicella in Wuxi, China. Varicella vaccination is urgently needed in routine childhood immunisation programs.