# High Effectiveness of the Changchun Baike Varicella Vaccine in a Real-World Outbreak Setting: An Observational Study from Yanji City, China

## TL;DR

A study in China found that the Changchun Baike varicella vaccine was highly effective in reducing chickenpox cases in real-world conditions.

## Contribution

The study provides real-world evidence of the high effectiveness of the Changchun Baike varicella vaccine, particularly the two-dose schedule.

## Key findings

- The varicella incidence rate in Yanji City dropped from 142.37 to 55.25 per 100,000 population between 2018 and 2024.
- The vaccine showed 98.0–99.0% effectiveness with one dose and 99.0% with two doses.
- The highest incidence was in the 10–14 age group, and the lowest in those aged ≥40.

## Abstract

Objectives: This study aimed to investigate the protective effect of the Changchun Baike varicella vaccine in Yanji City from 2018 to 2024. Methods: Varicella surveillance data from 2018 to 2024 and vaccination records from 2018 to 2020 were collected from the China Disease Prevention and Control Information System and analyzed. Results: In total, 2452 varicella cases were reported in Yanji from 2018 to 2024, with an average annual incidence rate of 62.71 per 100,000 population. Notably, the annual incidence rate decreased from 142.37 per 100,000 in 2018 to 55.25 per 100,000 population in 2024. Additionally, the highest and lowest incidence rates were observed in the 10–14 and ≥40 years age groups, respectively. Moreover, the vaccine demonstrated high protective effectiveness of 98.0–99.0% for one dose and 99.0% for two doses across the study period. These estimates were derived from propensity score-matched cohorts ranging from 686 to 6990 individuals (343 to 3495 matched pairs) across three overlapping observation periods (2018–2022, 2019–2023, and 2020–2024). Conclusions: The two-dose varicella vaccination schedule demonstrated superior protective efficacy compared with the single-dose schedule.