Study Title:

Early estimates of seasonal influenza vaccine effectiveness in Europe

Study Abstract

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.

Study Information

Kissling E, Valenciano M; I-MOVE Case-Control Studies Team.
Early estimates of seasonal influenza vaccine effectiveness in Europe among target groups for vaccination: results from the I-MOVE multicentre case-control study, 2011/12.
Euro Surveill.
2012 April
EpiConcept, Paris, France.

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