The proposed study design is a multicentre retrospective cohort design using data collected routinely from electronic health record (EHR) databases. The analysis included data from the resident community-dwelling population (i.e. excluding those living in nursing homes) ≥65 years of age and who belong to age-group for whom vaccination has been universally recommended at study enrolment (i.e. if vaccination with a booster was only recommended for individuals ≥80 years of age at a given month, VE corresponding to that month is only estimated in that group). Outcomes of interest include hospital admission due to COVID-19 and COVID-19-related death. Other data to be collected include socio-demographic (age, sex, region, country of birth, socioeconomic status), clinical (comorbidities) and COVID-19 vaccination (brand, number and dates of dose administration) variables.
The protocol outlines the agreed methods for VE analyses using national databases, and includes a plan for the pooled analysis of all participating country VE estimates. In most participating countries, vaccination campaigns begin between September and October 2024, thus a first early estimate of VE will be produced from January 2025 covering the early phase of the rollout (October to November 2024) followed by mid-year estimates in March and June 2025, and end of year estimates in September 2025.
This master protocol is primarily intended to guide the implementation of the ECDC-funded study in participating countries. However, ECDC encourages the conduct of VE studies, using this protocol as a basis, in countries that do not currently plan to participate in ECDC-funded studies. The use of common protocols will facilitate the comparability of results across studies, countries, sites, and time.