To further characterize the immune responses induced after an influenza vaccination performed either via the ID or the IM routes in two clearly distinct populations.

Objectives:

• To describe the immune response per age group and vaccine group after vaccination.
• To describe the safety of the vaccines per age group and per vaccine group after vaccination.

Inclusion Criteria :

• Aged 18 to 40 years (adults) or 60 to 85 years (elderly)
• 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 4 weeks after vaccination
• Entitlement to national social security.

Exclusion Criteria :

• For a woman of child-bearing potential, known pregnancy or positive urine pregnancy test
• Breast-feeding woman
• Participation in another clinical trial investigating a vaccine, drug, medical device or a 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 any of the vaccine components or history of a life-threatening reaction to the trial vaccine or to 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, which may interfere with the subject's ability to comply with trial procedures
• Receipt of blood or blood-derived products in the past 3 months, which 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 4 weeks following the trial vaccination
• Known Human Immunodeficiency Virus, Hepatitis B or Hepatitis C seropositivity
• Previous vaccination against Influenza in the previous 6 months
• Thrombocytopenia, bleeding disorder or anticoagulants in the 3 weeks preceding the inclusion contraindicating IM vaccination
• Subject deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent
• Febrile illness (oral temperature >=37.5°C) or moderate or severe acute illness/infection on the day of vaccination, according to investigator judgment