Pilot Protocol for a COVID-19 Vaccine Efficacy Study Using Health Data Registries

The end of 2019 saw the emergence of a new severe acute respiratory syndrome: coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19). Since December 31, 2019 and week 28 2022, 155,430,083 cases of COVID-19 (according to case definitions and testing strategies applied in affected countries) have been reported in the European Union, of which 1,124,471 death [1]. As of July 22, 2022, six COVID-19 vaccines – five of which are advanced protein-based – have received conditional marketing authorization within the European Union.
European Union/Economic Area (EU/EEA) by the European Commission, based on the scientific opinion of the European Medicines Agency (EMA): Comirnaty (BNT162b2), Spikevax (mRNA-1273), Vaxzevria (AZD1222) , Jcovden (Ad26.COV 2.5), and Nuvaxovid (NVX-CoV2373), and the non-spike protein (inactivated, adjuvanted) COVID-19 vaccine Valneva (VLA2001) [2,3].

In 2020, the European Commission highlighted the importance of continuously monitoring the safety and effectiveness of vaccines in the EU/EEA and called on the European Center for Disease Prevention and Control (ECDC) and the EMA to develop a structured post-authorisation surveillance platform for vaccines, prioritizing COVID-19 vaccines [4]. In November 2020, the European Commission proposed to the European Parliament and the Council of the EU a modification of the mandates of the EMA and the ECDC as part of its COVID-19 “lessons learned” package and the creation of a european health union, the two agencies jointly coordinate independent vaccine surveillance studies [5].

Accordingly, by the end of 2020, using lessons learned from other vaccine efficacy (VE) studies (e.g., influenza vaccine [6]), ECDC has started to build an infrastructure to perform COVID-19 VE studies. Monitoring COVID-19 VE over time aims to detect any reduction in vaccine performance that requires further investigation and public health action. The objective of the infrastructure is to build a system to routinely monitor VE and conduct studies in different settings and populations and using different regularly available or ad hoc data sources. Different outcomes will be considered, such as severe disease, moderate disease, or transmission and in various specific population groups (e.g. healthcare workers).

This pilot protocol for ECDC studies of VE of COVID-19 vaccines through routinely collected vaccination status and COVID-19 outcome data using health registries, version 1.0, presents the methodology that will be used to produce VE estimates using health data registries established in several studies. sites/countries (countries) in the EU/EEA. The study design in the current protocol is a retrospective cohort study using data routinely collected from electronic health record databases, selecting data from the community-dwelling resident population (i.e. i.e. excluding those living in closed institutions such as nursing homes and prisons) with no documented precedent. COVID-19 infection belonging to an age group for which vaccination was universally recommended at the time of the study. Outcomes include laboratory-confirmed SARS-CoV-2 infection (symptomatic or asymptomatic) or COVID-19-related hospitalization (all wards or intensive care units) or death. Other data to collect include sociodemographic (age, sex), clinical (comorbidities, history of SARS-CoV-2 infection) and COVID-19 vaccination variables (brand, number and dates of doses) variables. The protocol outlines agreed methods for analyzing available data related to COVID-19 and SARS-CoV-2 outcomes at both national and European level, including a plan for pooled analysis.

This pilot protocol is primarily intended to guide the implementation of an ECDC-funded first pilot study using routinely collected data, and includes a concise overview of the country systems included in the pilot study. ECDC encourages the conduct of VE studies, using this protocol as a basis, in countries that are not currently planning to participate in ECDC-funded studies. The use of consistent protocols will facilitate comparability of results between study sites/studies.

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