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The problem
Intervention: COVID-19 vaccination with original monovalent vaccine, monovalent booster, and bivalent booster doses
Who it was tested with: Children and adolescents aged 5-17 years residing in 11 large cities in Japan (1,908,012 records included).
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.
"A retrospective cohort study was conducted targeting residents aged 5-17 years in 11 cities in Japan. Combining the national SARS-CoV-2 surveillance record and vaccination registry, Cox proportional hazard regression analyses were performed to estimate the effectiveness of the original monovalent vaccine against Omicron infection compared with unvaccinated." The study used a cohort design with comparison between vaccinated and unvaccinated groups, applying regression analysis to adjust for confounders, which constitutes an experimental design approach using observational data.
Study limited to Omicron BA.5 variant; conducted in 11 urban centers in Japan which may not represent all populations; retrospective design; waning of protection may be influenced by population immunity dynamics and variant evolution
Across countries and designs
11 studies · 12 countries
