Peer-reviewed article
The Impact and Effectiveness of a Two-Dose Varicella Immunization Program Among School Children: Evidence from Quasi-experimental Analyses.
Huiqiao Gu, Xu Xie, Qiuying Lv, Yuantian Cui, Ziyan Lu et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study evaluated a free two-dose varicella vaccination program introduced in Shenzhen, China for school-aged children. Using official immunization and surveillance data, researchers compared vaccinated and unvaccinated cohorts to measure the program's impact. The program reduced varicella disease cases by 23%, increased first-dose vaccination coverage by 35%, and second-dose coverage by 98%. Two-dose vaccination provided 75% additional protection compared to single-dose vaccination.
Key points
- The publicly funded two-dose varicella program reduced disease incidence by 22.96% in eligible cohorts relative to ineligible cohorts
- First-dose vaccine coverage increased by 34.97% and second-dose coverage increased by 98.05% following the policy
- Two-dose vaccination schedule provided 75.19% relative vaccine effectiveness against breakthrough infection after a single dose
- The program demonstrates the superior protection of two-dose versus single-dose varicella vaccination regimens
- Potential underreporting and misdiagnosis of varicella cases may have underestimated the true disease burden
Limitations
The study relies on mandatory case reporting systems which are subject to underreporting and misdiagnosis, potentially underestimating true varicella incidence. The analysis is limited to one city (Shenzhen) and may not be generalizable to other regions with different healthcare systems or population characteristics.
Abstract
INTRODUCTION: Varicella, caused by the varicella zoster virus, poses a significant public health challenge, particularly among children. To address this, the city of Shenzhen, China, introduced a publicly funded vaccination program offering free two-dose varicella vaccines to eligible school-aged cohorts. This study aims to evaluate the program's impact on disease incidence, vaccination uptake, and the comparative effectiveness of two-dose versus single-dose regimens. METHODS: We used the individual-level data from official immunization and surveillance systems, covering pupils born between 1 September 2014 and 31 August 2015. Applying a difference-in-differences approach, we compared the disease incidence and vaccination uptake between the eligible cohort and ineligible cohort. Additionally, to further evaluate the effectiveness of the two-dose vaccination schedule, we implemented a regression discontinuity design using the policy cutoff date. RESULT: The policy reduced varicella incidence by 22.96% (95% CI 8.98-34.79%, p < 0.05) in the eligible cohort relative to the ineligible one, while boosting first- and second-dose coverage by 34.97% (95% CI 28.19-2.11%, p < 0.05) and 98.05% (95% CI 91.98-104.31%, p < 0.05), respectively. The regression discontinuity design indicated that the two-dose schedule conferred 75.19% (95% CI 70.62-79.06%) relative vaccine effectiveness against breakthrough varicella after a single dose. This study's main limitation is that, while reporting of varicella cases is mandatory, underreporting and misdiagnosis remain possible, potentially underestimating true incidence. CONCLUSIONS: These findings demonstrate the program's success in reducing disease burden and enhancing immunization rates, underscoring the superior protection of two-dose vaccination and providing strong evidence for policymakers to expand such initiatives.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Publicly funded two-dose varicella vaccination program offered free to eligible school-aged children
- Population
- School children in Shenzhen, China born between September 1, 2014 and August 31, 2015; eligible cohort received free vaccines while ineligible cohort did not
Key finding
Varicella incidence reduced by 22.96% (95% CI 8.98-34.79%) in eligible cohort relative to ineligible cohort