[Evaluation of varicella vaccine effectiveness among children aged 1-14 years in Weifang City: a case-control study].

Based on the reports from the Chinese Disease Prevention and Control Information System, 177 varicella cases among children aged 1 to 14 in Weifang City from 2022 to 2024 were selected as the case group. Through the Weifang Immunization Planning Information Platform, 708 healthy children were individually matched at a 1∶4 ratio by age, sex, and town/street and included as controls. A conditional multivariable logistic regression model was used to estimate the vaccine effectiveness (VE) of the varicella vaccine, while restricted cubic splines (RCS) were applied to analyze the dynamic changes in VE after the last dose. Results showed that the overall VE was 80.72% (95%CI: 69.16%-87.95%), with two-dose vaccination providing significantly higher protection (91.63%) than one dose (50.96%). The VE after the last dose exhibited an initial increase followed by a decline over time. In conclusion, the varicella vaccine demonstrates strong effectiveness against varicella; therefore, a two-dose vaccination strategy is recommended and should be incorporated into routine immunization programs.