Early estimates of seasonal influenza vaccine effectiveness in Europe

To provide an early estimate of 2011/12 influenza vaccine effectiveness (VE), we conducted a multicentre case-control study based on seven sentinel surveillance networks. We included influenza-like illness cases up to week 7/2012 from the vaccination target groups, swabbed less than eight days after symptom onset. Laboratory-confirmed influenza A(H3) cases were compared to negative controls. Adjusted VE was 43% (95% confidence interval: -0.4 to 67.7), suggesting low to moderate VE against influenza A(H3) in the early 2011/12 season.

An update on this information was provided by the Lancet in January of 2013 (The Lancet Infectious Diseases, Volume 13, Issue 1, Pages 7 - 9, January 2013 ):
The Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) project—a publicly funded network supported by the European Centre for Disease Prevention and Control (ECDC) and EU member states—monitors the effectiveness of influenza vaccines every year, and in April, 2012, showed a low early season effectiveness of 43% of the 2011—12 influenza vaccine in the risk groups in eight European countries. Analyses derived from late in the season suggested this effectiveness had fallen to less than 10% for the risk groups. These especially low estimates of effectiveness could be attributed to difficulties with the antigenicity of the influenza A subtype H3N2 antigen for the vaccine versus the dominant viruses, a drawback which WHO vaccine recommendations for 2012—2013 intend to remedy. However, the 2011 review and I-MOVE studies show that, in Europe, seasonal vaccine effectiveness in the old and clinical risk groups is always less than 70%. Additionally, WHO reviews and recommendations generally only address virological issues and rarely pay attention to estimates of effectiveness. Poor performance of the seasonal vaccines undermines Europe's other strengths in influenza prevention.