The study is designed to assess the immunogenicity and safety of one booster vaccination with 45 μg of a recombinant H5N1 influenza (A/Indonesia/05/2005) HA vaccine in healthy young adults, previously primed with a two-vaccination of 3 different doses of a recombinant H5N1 influenza (A/Vietnam/1203/2004) HA vaccine in a priming study (JPIP501-01a, NCT00980447).

Inclusion Criteria:

• Subjects who completed a priming study (JPIP501-01a, NCT00980447)
• Male and female healthy adults
• Written informed consent obtained from the subject before study entry

Exclusion Criteria:

• History of H5N1 influenza or vaccination of other H5N1 influenza vaccines
• Clinically diagnosed cardiovascular, hematological, psychological, neurological, hepatic, renal, pulmonary (including asthma), endocrinological or gastrointestinal disorder
• Confirmed immune deficiency conditions, or diagnosed autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus
• Severe allergic reactions or anaphylaxis to foods or drugs (including vaccines)
• Treatment with disallowed drugs including other study drugs
• Pregnant or nursing (lactating) women

Other protocol-defined inclusion/exclusion criteria may apply