To evaluate the vaccine effectiveness (VE) of single-dose and two-dose varicella vaccine (VarV) among senior high school students during a varicella outbreak in China.
Approach:
Study Design: A retrospective cohort study was conducted among students in a senior high school in China during a varicella outbreak from July 23 to November 8, 2024.
Data Collection: The study surveyed the history of varicella disease, immunization history of VarV, and incidence during the outbreak among all students.
Statistical Analysis: Kaplan–Meier methods were used to estimate cumulative varicella-free survival rates, and logistic regression was performed to identify factors associated with varicella infection.
Key Findings:
Overall varicella attack rate was 6.29% among 1,862 students.
Single-dose VarV coverage was 28.24%, and two-dose coverage was 66.23%.
Vaccine effectiveness (VE) was 32.14% (−54.37%-70.17%) for 1-dose recipients and 94.74% (88.62%-97.57%) for 2-dose recipients compared to unvaccinated individuals.
Post-exposure vaccination VE was 90.15% (68.53%-96.92%) among unvaccinated students and 94.88% (89.47%-97.51%) among those who had received 1 dose.
Interpretation:
A single dose of varicella vaccine provides limited long-term protection, while a two-dose regimen offers robust and sustained effectiveness.
Limitations:
The study is limited to a single high school outbreak, which may affect generalizability.
Potential biases in self-reported vaccination status.
Conclusion:
A single dose of varicella vaccine provides limited long-term protection among high school students, whereas a two-dose regimen offers robust and sustained effectiveness.
