Immunogenicity and Safety of the Inactivated, Split-Virion Influenza Vaccine, Northern Hemisphere 2008-2009 Formulation

Inclusion Criteria : * Aged 18 to 60 years or 61 years and older on the day of inclusion * Provision of a signed informed consent * Able to attend all scheduled visits and comply with all trial procedures * For a woman of child-bearing potential: avoid becoming pregnant (use of an effective method of contraception or abstinence) for at least 4 weeks prior to vaccination, until at least 21 days after vaccination Exclusion Criteria : * For a woman of child-bearing potential, known pregnancy or positive urine pregnancy test at visit 01 * Febrile illness (temperature ≥ 37.5°C) or moderate or severe acute illness/infection on the day of vaccination, according to Investigator judgment * Breast-feeding woman * Participation in another clinical trial investigating a vaccine, drug, medical device, or medical procedure in the 4 weeks preceding the trial vaccination * Planned participation in another clinical trial during the present trial period * Known or suspected congenital or acquired immunodeficiency, immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term systemic corticosteroids therapy * Known systemic hypersensitivity to egg proteins, chick proteins, neomycin, formaldehyde and octoxinol 9, or to any of the vaccine components, or history of a life-threatening reaction to the trial vaccine or a vaccine containing any of the same substances * Chronic illness at a stage that could interfere with trial conduct or completion, in the opinion of the Investigator * Current alcohol abuse or drug addiction that may interfere with the subject's ability to comply with trial procedures * Receipt of blood or blood-derived products in the past 3 months, that might interfere with the assessment of immune response * Receipt of any vaccine in the 4 weeks preceding the trial vaccination * Planned receipt of any vaccine in the 3 weeks following the trial vaccination * Previous vaccination against influenza in the previous 6 months * Thrombocytopenia, bleeding disorder or anticoagulants in the 3 weeks preceding inclusion contraindicating intramuscular vaccination * Known Human Immunodeficiency Virus (HIV), Hepatitis B surface antigen or Hepatitis C seropositivity * Subject deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent.