On the 26 October 2011, The Lancet Infectious Diseases published a systematic review and a meta-analysis, combining the results of several studies undertaken on influenza vaccine effectiveness.
Overall the influenza vaccine was effective in the majority of the seasons and of the studies. Acknowledging the burden of influenza, the authors confirmed that vaccination was the most effective way of preventing it. However, they noted what many other independent groups, including ECDC and its collaborators, have found: influenza vaccines do not give complete protection to all who receive them. The authors also agree with ECDC views that there are critical gaps in high quality evidence for the effectiveness of licensed influenza vaccines especially for some age groups.
As highlighted in the ECDC Scientific Advance published today, at European level, ECDC has been funding and, with Epiconcept, coordinating the Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE). These are undertaken with many Member States to monitor seasonal and pandemic influenza vaccine effectiveness in ten European Union countries. I-MOVE monitors seasonal and pandemic vaccine effectiveness on a routine basis. Results for the seasons 2008/09 and 2009/2010 have been published and are included in the literature review published in The Lancet Infectious Diseases. The 2010-2011 results have been accepted for publication and will be published soon.
Overall, the results from the I-MOVE studies are broadly in line with the ones published by The Lancet Infectious Diseases in the mentioned article. In general, influenza vaccine effectiveness as measured in the multicentric I-MOVE studies ranged from around 59% in 2008/2009 when only individuals older than 65 years were included to around 72% during the 2009/10 pandemic season when all age-groups were included.
ECDC notes that although influenza vaccines do not provide a complete protection against influenza virus but they are the most effective preventive measure. Development of more effective vaccines is certainly to be considered by ECDC to be a priority for researchers and vaccine manufacturers.
Through the studies undertaken by the I-MOVE collaboration, ECDC and its partners in EU Member States have been actively contributing to bridge the gaps in evidence highlighted by the authors of the article published by The Lancet Infectious Diseases. Since influenza viruses continue to change every season, also post-marketing studies of vaccine effectiveness should continue in Europe the future in order to monitor possible variations. These studies are important to inform policymakers and the public of the contemporary state of performance of these important vaccines.