A Dose Ranging Safety and Immunogenicity Study of GlaxoSmithKline (GSK) Biologicals' GSK1557484A Vaccine in Children 6 to Less Than 36 Months of Age

The purpose of this study is to assess the safety and immunogenicity of different formulations of GSK Biologicals' influenza candidate vaccine GSK1557484A, in children 6-35 months of age.

Safety and immunogenicity of different formulations administered as a 2-dose schedule in children 6-35 months of age will be evaluated. In addition, the quality of the 2-dose priming will be assessed through the anamnestic response elicited by an antigen challenge (unadjuvanted H5N1) administered 12 months later. The persistence of the immune response approximately 12 months (Day 385) after dose 2 will also be evaluated.

Subjects from each group will be enrolled into the CMI sub-cohort comprising of approximately 100 subjects. Within the participating country(ies), these subjects will be enrolled in only selected/qualified sites.

Eligibility Criteria:
Inclusion Criteria:

* Subject's parent(s)/ Legally Acceptable Representative(s) \[LAR(s)\] who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
* Male or female children 6 months to less than 36 months old at the time of the first vaccination. Children who are not 36 months old as of Day 0, the day of first vaccine dose under this protocol, can be enrolled.
* Written informed consent obtained from the parent(s)/legally acceptable representative(s) \[LAR(s)\] of the subject prior to performance of any study specific procedure.
* Healthy subjects as established by medical history and standard physical examination before entering into the study.
* Born full-term to be confirmed by interview with parent/LAR or available medical records.

Exclusion Criteria:

* Child in care.
* Medical history of physician-confirmed infection with an H5N1 virus.
* Previous vaccination at any time with an H5N1 vaccine.
* Concurrently participating in another clinical study, or use of an investigational or a non-registered vaccine, pharmaceutical product, or device within 30 days preceding the first dose of study vaccine, or planned use during the study period.
* Presence in the parent(s) / LAR(s) of evidence of substance abuse or of neurological or psychiatric diagnoses which, even if stable, are deemed by the investigator to render the parent(s)/LAR(s) unable/unlikely to provide accurate safety reports.
* Acute disease and/or fever at the time of enrolment.
* Administration of immunoglobulins, any blood products, or long-acting immune-modifying drugs during the period starting 3 months before the first dose of study vaccine, or planned administration during the study period.
* History of any neurological disorders or seizures, or Guillain-Barré Syndrome.
* Diagnosed with excessive daytime sleepiness or narcolepsy; or history of narcolepsy in a subject's parent or sibling.
* Administration of an inactive vaccine within 14 days or of a live attenuated vaccine within 30 days before the first vaccination.
* Planned administration of any vaccine not foreseen by the study protocol between Day 0 and Day 42 or planned administration of an inactive vaccine within 14 days or of a live attenuated vaccine within 30 days before through 30 days after the booster vaccination. Note: routine vaccinations may be provided on Day 42 after all study assessments have been performed.
* History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine; a history of anaphylactic-type reaction to consumption of eggs; or a history of severe adverse reaction to a previous influenza vaccine.
* Any medical condition that in the judgment of the investigator would make intramuscular injection unsafe.
* Chronic administration of immunosuppressants or other immune-modifying drugs during the period starting six months prior to the first vaccine. For corticosteroids, this will mean a dose of prednisone or equivalent of \> 2 mg/kg/day of body weight or ≥ 20 mg/day (for persons who weigh ≥ 10 kg). Inhaled and topical steroids are allowed.
* Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination.
* Family history of congenital or hereditary immunodeficiency.
* Major congenital defects.
* Any condition which, in the opinion of the investigator, prevents the subject from participating in the study.