Epidemiological analysis and exploration of prevention and control strategies for breakthrough cases of varicella in Jiangsu Province China.

To analyze the epidemiological characteristics of breakthrough varicella cases in Jiangsu Province and provide a basis for optimizing prevention and control strategies. Data were integrated from the Chinese Information System for Disease Control and Prevention and the Jiangsu Province Comprehensive Vaccination Service Management System. Since the implementation of the policy of free two-dose Varicella vaccination (Varicella Vaccine, VarV) for children aged 1 to 6 in 2023, the average annual incidence rate of varicella in Jiangsu Province (59.42 per 100,000) has been significantly lower than that from 2019 to 2022 (103.70 per 100,000), with a particularly notable decline in the incidence rate among children aged 1 to 6. From 2023 to 2024, the proportion of breakthrough cases of varicella in Jiangsu Province reached 26.2%. The proportion of cases that broke through after one dose of vaccination was 22.4%, and the interval between the onset of the disease and the last vaccination was mostly more than six years. The proportion of those who received two doses was 3.8%. The protective effect of one dose of the varicella vaccine in the 2022-303 birth cohort was 95.70%. Vaccination has effectively reduced the incidence of varicella in Jiangsu Province, but breakthrough cases still account for a certain proportion. It is suggested that the two-dose vaccination strategy be optimized in a targeted manner based on the epidemiological characteristics of breakthrough cases.