Inclusion Criteria :

• Aged 18 to 60 years on the day of inclusion.
• Informed consent form signed.
• Able to attend all scheduled visits and to comply with all trial procedures.
• For a woman, inability to bear a child or negative urine pregnancy test at the first visit.

Exclusion Criteria :

• Systemic hypersensitivity to egg proteins, chick proteins, or any of the vaccine components, in particular, neomycin, formaldehyde, and octoxinol 9, or history of a life-threatening reaction to the trial vaccine or a vaccine containing the same substances.
• Febrile illness (oral temperature >= 37.5°C, or rectal equivalent temperature >= 38.0°C) on the day of inclusion.
• Participation in another clinical trial in the 4 weeks preceding the trial vaccination.
• Planned participation in another clinical trial during the present trial period.
• 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.
• Unstable chronic illness (defined as illness requiring hospitalization or a clinically significant change in medication in the 12 weeks prior to inclusion) at a stage that could interfere with trial conduct or completion.
• Current abuse of alcohol or drug addiction that may interfere with the subject's ability to comply with trial procedures.
• Blood or blood-derived products received in the past 3 months.
• Any vaccination in the 4 weeks preceding the trial vaccination.
• Vaccination planned in the 4 weeks following the trial vaccination.
• Previous vaccination against influenza (in the previous 6 months).
• Thrombocytopenia or bleeding disorder contraindicating intramuscular vaccination.
• Subject deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized without his/her consent.