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.

Inclusion Criteria:

• Healthy female and male adults aged >60 years on the day of enrollment
• Written informed consent
• Females with confirmed menopause (postmenopausal is defined as 12 months with no menses without an alternative medical cause)

Exclusion Criteria:

• Acute exacerbation of bronchopulmonary infection (cough, sputum, lung findings) or other acute disease
• Acute febrile illness (≥38.0 °C)
• Prior vaccination with an influenza vaccine for season 2011/2012
• Known hypersensitivity to any vaccine component
• Previous history of a serious adverse reaction to influenza vaccine
• History of egg protein allergy or severe atopy
• Known blood coagulation disorder
• Chronic (longer than 14 days) administration of immunosuppressants or other immune-modifying drugs within 6 months before the first dose of the study vaccine, including oral corticosteroids in dosages of ≥0.5 mg/kg/day prednisolone or equivalent (inhaled or topical steroids are allowed)
• Known immunodeficiency (including leukemia, HIV seropositivity) or cancer
• Investigational medicinal product received in the past 3 months (90 days)
• Treatment with immunoglobulins or blood transfusion(s) received in the past 3 months (90 days)
• Participation in another clinical trial
• Employee at the investigational site or relative of the investigator
• Anticipated non-compliance with study procedures