Increase in reported adverse events following seasonal influenza vaccination among the French armed forces, 2008-2009: Possible role of stimulated reporting and background cases of influenza-like infection

The increase in seasonal influenza VAE in late 2009 mainly involved non-serious events, and could reflect stimulated reporting in the context of the A(H1N1)pdm09 pandemic. VAE reporting rates were highest during influenza epidemic periods, which could be explained by VAE being wrongly attributed to the vaccine when symptoms could reflect coincident background cases of viral infection.