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The problem
Intervention: Publicly funded two-dose varicella vaccination program offered free to eligible school-aged children
Who it was tested with: School children in Shenzhen, China born between September 1, 2014 and August 31, 2015; eligible cohort received free vaccines while ineligible cohort did not.
Children or communities are compared with a group that did not receive the intervention, or followed over years. This is the design that best separates what the intervention did from everything else that changed.
"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." This quasi-experimental design with a comparison group between cohorts separated by policy implementation date provides robust evidence of program effectiveness.
Varicella case reporting is mandatory but subject to underreporting and misdiagnosis, potentially underestimating true disease incidence. Study conducted in one city and results may not be generalizable to other regions.
Across countries and designs
5 studies · 3 countries
