Protocol for a COVID-19 vaccine effectiveness multi-country cohort study in the paediatric population aged 5–17-years using electronic health records in EU/EEA countries

The study design is a retrospective cohort study using data from paediatric populations aged under 18 years old and eligible for COVID-19 vaccination, collected routinely in electronic health records databases. The study started at the beginning of the vaccination campaign for each age cohort and country (5-11 years old, 12-17 years old) and ended one year after. The outcome of interest is hospital admission due to COVID-19. Data collected, besides the outcome of interest, included sociodemographic (age, sex), clinical (comorbidities, previous history of severe acute respiratory syndrome – coronavirus 2 (SARS-CoV-2) infection) and COVID-19 vaccination history (brand, number and dates of dose administration).

The protocol outlines the methodology for analysing data at the country level and includes a plan for the pooled analysis. This master protocol was primarily intended to guide the implementation of one study within the VEBIS project. However, ECDC encourages, using this protocol as a basis to conduct vaccine effectiveness studies in countries that do not currently plan to participate in ECDC-funded studies. Consistent protocols will facilitate comparability of results across studies, countries and sites.