Pilot protocol for a COVID-19 vaccine effectiveness study using health data registries

Public health guidance

European Centre for Disease Prevention and Control. Pilot protocol for a COVID-19 vaccine effectiveness study using health data registries. Stockholm: ECDC; 2022.

The overall aim of the project based on this protocol is to monitor the real-time performance of COVID-19 vaccines in the community-dwelling resident population in EU/EEA countries in order to detect any signal in terms of reduced vaccine effectiveness, so that public health vaccine recommendations may be adjusted accordingly. To achieve this aim, hazard ratio or rate ratio of outcomes of interest will be estimated using information routinely collected in various registries, including vaccination, population and health databases, and using data linkage.

Executive Summary

The end of 2019 saw the emergence of a novel severe acute respiratory syndrome: coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19). Since 31 December 2019 and as of week 28 2022, 155 430 083 cases of COVID-19 (in accordance with the applied case definitions and testing strategies in the affected countries) have been reported in the European Union, including 1 124 471 deaths [1]. As of 22 July 2022, six COVID-19 vaccines – five of which are spike protein-based – had been given conditional marketing authorisation within the European
Union/European 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-based COVID-19 vaccine (inactivated, adjuvanted) Valneva (VLA2001) [2,3].

In 2020, the European Commission emphasised the importance of continuously monitoring the safety and effectiveness of vaccines in the EU/EEA, and called on the European Centre for Disease Prevention and Control (ECDC) and EMA to develop a structured post-authorisation monitoring platform for vaccines, prioritising COVID-19 vaccines [4]. In November 2020, the European Commission proposed to the European Parliament and the Council of the EU a change to the mandates of EMA and ECDC in the context of its COVID-19 ‘lessons learned’ package and the creation of a European Health Union, empowering the two agencies to jointly coordinate independent vaccine monitoring studies [5].

As a result, at the end of 2020, utilising the lessons learned from other vaccine effectiveness (VE) studies (e.g influenza vaccine [6]), ECDC started building infrastructure to perform COVID-19 VE studies. The monitoring of COVID-19 VE over time aims to detect any reduction in vaccine performance that requires further investigation and public health action. The aim of the infrastructure is to build a system to regularly monitor VE and perform studies in different settings and populations and using different routinely available or ad hoc data sources. Different outcomes will be looked at such as severe disease, moderate disease, or transmission and in various and other 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 established health data registries across several study sites/countries (countries) in the EU/EEA. The study design in the current protocol is a retrospective cohort study using data collected routinely in electronic health records databases, selecting data on the resident community-dwelling population (i.e. excluding those living in closed institutions such as nursing homes and prisons) without any documented previous COVID-19 infection who belong to an age group for whom vaccination has been universally recommended at the time of the study. Outcomes include laboratory-confirmed SARS-CoV-2 infection (either symptomatic or asymptomatic) or COVID-19-related hospital admission (either all wards or intensive care units) or death. Other data to be collected include sociodemographic (age, sex), clinical (comorbidities, previous history of SARS-CoV-2 infection) and COVID-19 vaccination variables (brand, number, and dates of doses). The protocol outlines the agreed methods for analysing available data related to COVID-19 and SARS-CoV-2 outcomes both at country level and at European level, including a plan for the pooled analysis.

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