This study is to identify the preferred vaccine dosage (of antigen and adjuvant) and schedule (one or two administrations) of the cell-derived H1N1sw monovalent vaccine in healthy children/adolescents based on European Medicines Agency's Committee for Medicinal Products for Human Use (EMEA/CHMP) criteria, and safety and tolerability.

This is a multi-center, randomized, single-blind, dose-ranging study. Subjects were randomized at a 1:1 ratio to receive either 3.75μg of cell-derived H1N1sw vaccine formulated in half (i.e., half the content of the European-licensed adjuvanted seasonal influenza vaccine) MF59 adjuvant (3.75_halfMF59) or 7.5μg of cell-derived H1N1sw vaccine formulated with full MF59 (7.5_fullMF59). Subjects were not informed of their allocated doses. Two vaccinations were administered IM three weeks apart. Subjects in both the vaccine groups were stratified into three age strata: 6 to 35 months, 3 to 8 years and 9 to 19 years. Blood samples were collected at day 1 (baseline), three weeks after the first vaccination (day 22) and three weeks after the second vaccination (day 43). Sera were tested by Hemagglutination Inhibition (HI) and Microneutralization (MN) assays. Local and systemic reactions were collected for the first week following each injection using Diary Card (i.e., day 1 to day 7 and day 22 to day 28). All adverse events (AE), serious adverse events (SAE), and AEs that led to withdrawal from the study and related prescription medications were collected for the entire study period.

Inclusion Criteria:

• Healthy Japanese aged 6 months to 19 years

Exclusion Criteria:

• History of anaphylaxis, serious vaccine reactions, hypersensitivity to vaccine viral proteins or excipients
• Administration of adjuvanted influenza vaccine or suspected influenza disease within 3 month prior to study start
• Administration of any other vaccines within 4 weeks prior to enrollment expect for seasonal influenza vaccines within 1 week
• History of progressive or severe neurological disorders