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The problem
Intervention: Influenza vaccination program with national immunization coverage
Who it was tested with: Children aged 6 months to 13 years and adults aged 65 years and older in South Korea.
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.
"VE was estimated using both a target trial emulation (TTE)-based retrospective cohort design to assess age-specific outcomes and an interrupted time series (ITS) method with dynamic cohort to evaluate time-varying protection." This quasi-experimental design with comparison groups using national administrative data provides strong evidence of vaccine effectiveness in a real-world population setting.
The study uses retrospective cohort design rather than randomized controlled trials. The analysis does not separately report outcomes by specific vaccine type or viral strain characteristics. Causality cannot be fully established due to potential unmeasured confounding in observational data.
Across countries and designs
3 studies · 3 countries
