A study to evaluate the humoral immune response 3 weeks after vaccination with Inflexal V according to the CHMP criteria in elderly subjects for the 2011/2012 WHO recommended vaccine strains, to evaluate immunogenicity parameters 6 months after vaccination for the 3 vaccine strains and to assess the cross-protection against 4 selected circulating heterogeneous A/H1N1 influenza strains 3 weeks after influenza vaccination versus baseline.