Effectiveness of One- and Two-Dose Varicella Vaccination Among Children and Adolescents Aged 0-18 Years - Chaoyang District, Beijing, China, 2007-2025.

INTRODUCTION

Varicella is a highly contagious respiratory disease caused by the varicella-zoster virus that predominantly affects children and is prone to outbreaks in congregate settings. This study evaluated the effectiveness of varicella vaccination among children and adolescents aged 0-18 years in Chaoyang District and examined factors associated with infection risk.

METHODS

A retrospective cohort study was conducted among 551,980 children and adolescents born between 2007 and 2025 using varicella surveillance data from the Chaoyang District Center for Disease Control and Prevention. Incidence rates were calculated, and vaccine effectiveness was estimated using Cox proportional hazards models.

RESULTS

Among the 551,980 participants, 9,170 varicella cases were identified. The incidence rate was 20.79 per 1,000 person-years (PY) in the unvaccinated group, 2.28 per 1,000 PY in the one-dose group, and 0.34 per 1,000 PY in the two-dose group. Increasing vaccine dose number was significantly associated with a lower risk of infection. The cumulative incidence of varicella was lowest and most stable in the two-dose group during follow-up. Vaccine effectiveness (VE) was 96.8% [95% confidence interval (CI): 95.7%, 97.6%] for one-dose vaccination and 98.2% (95% CI: 97.9%, 98.5%) for two-dose vaccination. Males accounted for 56.2% of cases and had a slightly higher infection risk than females.

CONCLUSION

Two doses of varicella vaccine provided strong protection against varicella. These findings support efforts to increase two-dose vaccination coverage and optimize varicella immunization schedules.