Core protocol for ECDC studies of COVID-19 vaccine effectiveness against hospitalisation with Severe Acute Respiratory Infection, laboratoryconfirmed with SARS-CoV-2 or with seasonal influenza – Version 2.0

This core protocol for ECDC studies of vaccine effectiveness against hospitalisation with Severe Acute Respiratory Infection laboratory-confirmed with SARS-CoV-2 or with influenza, version 2.0, represents an update to the main elements for a multi-country hospital-based study of COVID-19 vaccine effectiveness in patients hospitalised with Severe Acute Respiratory Infection (SARI), already published as version 1.0.