Protocols for cohort database studies to measure influenza vaccine effectiveness in the EU and EEA Member States

Changes in the genetic makeup of the influenza virus call for new vaccines on an annual basis. Assessing and monitoring the effectiveness of pandemic vaccines is essential once they become available. Although strain-specific pandemic vaccines are expected to be effective, the early availability of vaccine effectiveness estimates could make a valuable contribution to the success of vaccination campaigns. The generic study protocols presented here summarise all relevant methodological issues related to conducting cohort database studies aimed at measuring vaccine effectiveness for seasonal and A(H1N1)v influenza. All protocols were developed as part of an ECDC project entitled I-MOVE (Influenza Monitoring of Vaccine Effectiveness). Based on these protocols, a number of specific studies will be conducted during the current influenza A(H1N1)v virus pandemic.