Study of Sanofi Pasteur's Intradermal Influenza Vaccine (IDflu™) in Adults and Elderly in Korea

Inclusion Criteria: * Aged 18 years and over on the day of inclusion * Informed consent form has been signed and dated * Able to attend all scheduled visits and to comply with all trial procedures * For a woman of childbearing potential, use of an effective method of contraception or abstinence from at least 4 weeks prior to vaccination until at least 4 weeks after vaccination. Exclusion Criteria: * Known systemic hypersensitivity to eggs, chicken proteins, neomycin, formaldehyde and octoxynol-9, or to any of the vaccine components, or history of a life-threatening reaction to the vaccine used in the trial or to a vaccine containing any of the same substances * Known pregnancy, or a positive urine pregnancy test * Currently breastfeeding a child * History of seasonal influenza vaccination within the previous 6 months (other than pandemic H1N1 influenza vaccine) * Receipt of an influenza vaccine (either seasonal or pandemic vaccine) in a clinical trial within the previous 12 months * Known or suspected congenital or acquired immunodeficiency, resulting for example from: end-stage renal disease requiring dialysis; active neoplastic disease or active hematologic malignancy; receipt of immunosuppressive therapy or other immune-modifying drugs such as, but not limited to anti-cancer chemotherapy or radiation therapy within the preceding 6 months, or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months) * History of seropositivity for Human Immunodeficiency Virus (HIV), Hepatitis B, or Hepatitis C * Receipt of blood or blood-derived products in the past 3 months, which might interfere with assessment of the immune response * Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion * History of thrombocytopenia, contraindicating intramuscular (IM) vaccination * Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating IM vaccination, under the investigator's judgment * 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 * 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 * Deprived of freedom by an administrative or court order, or in an emergency setting, or hospitalized involuntarily * Current alcohol abuse or drug addiction that might interfere with the ability to comply with trial procedures * Identified as employees of the Investigator or study department, with direct involvement in the proposed study or other studies under the direction of that Investigator or study department as well as family members (i.e., immediate, husband, wife and their children, adopted or natural) of the employees or the Investigator