Safety and Immunogenicity of 2 Formulations of an Intramuscular A/H5N1 Pandemic Influenza Vaccine in Children

Inclusion Criteria : All subjects: * Able to attend all scheduled visits and to comply with all trial procedures. Children/Adolescents aged ≥ 2 years to \< 18 years: * Aged ≥ 2 years to \< 18 years on the day of inclusion. * Informed Consent Form signed by one parent or another legal representative and by an independent witness if the parent/legal representative is illiterate. * For a female, inability to bear a child or negative urine pregnancy test (as applicable). * For a female of child-bearing potential, use of an effective method of contraception or abstinence for at least 4 weeks prior to the first vaccination and at least 4 weeks after the last vaccination (as applicable). Infants/toddlers aged ≥ 6 months to \< 2 years: * Aged ≥ 6 months to \< 2 years on the day of inclusion. * Born at full term of pregnancy (≥ 37 weeks) with a birth weight ≥ 2 kg. * Informed Consent Form signed by one parent/legally acceptable representative and an independent witness if the parent/legally acceptable representative is illiterate. * Subject who completed vaccination according to the national immunization schedule. Exclusion Criteria : All subjects: * Participation in another clinical trial in the 4 weeks preceding the first 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 corticosteroid therapy. * Systemic hypersensitivity to any of the vaccine components or history of life threatening reaction to the trial vaccine or a vaccine containing the same substances (egg proteins, chick proteins, thimerosal, aluminum, neomycin, formaldehyde, and octoxinol 9). * Chronic illness at a stage that could interfere with trial conduct or completion. * Blood or blood-derived products received in the past 3 months. * Any vaccination in the 4 weeks preceding the first trial vaccination. * Vaccination planned in the 4 weeks following any trial vaccination. * History of the H5N1 infection (confirmed either clinically, serologically or virologically). * Known HIV, Hepatitis B (HBsAg) or Hepatitis C seropositivity. * Previous vaccination with an avian flu vaccine. * Subject at high risk of the H5N1 infection during the trial. * Thrombocytopenia or bleeding disorder contraindicating IM vaccination. * Febrile illness (rectal equivalent temperature ≥ 38.0°C) on the day of inclusion. Children/Adolescents aged ≥ 2 years to \< 18 years: * Breast-feeding mothers. * Current alcohol abuse or drug addiction that may interfere with the subject's ability to comply with trial procedures (if applicable, depending on the subject's age). Infants/toddlers aged ≥ 6 months to \< 2 years: * History of seizures.