• Vaccine-homologous virus antibody response [ Time Frame: Prior to and 10 days after Dose 2 and/or Dose 3 ] [ Designated as safety issue: No ]
• The occurrence of specifically-solicited local and general signs and symptoms [ Time Frame: during 7-day follow-up period after each dose of vaccine or placebo. ] [ Designated as safety issue: No ]
• The occurrence of all unsolicited adverse events [ Time Frame: during a 42-day follow-up period after each vaccination. ] [ Designated as safety issue: No ]
• The occurrence of serious adverse events and medically-attended events [ Time Frame: during the entire study period ] [ Designated as safety issue: No ]

• Vaccine-homologous virus antibody response. [ Time Frame: Prior to and 10 days after Dose 2 ] [ Designated as safety issue: No ]
• Change in the proportion of subjects with antibody titers ≥ specified cut-off [ Time Frame: Day 182 to Day 192 or Day 365 to Day 375; Day 182 to Day 224 or Day 365 to Day 407 ] [ Designated as safety issue: No ]
• Geometric mean fold-rise in antibody titers [ Time Frame: Day 182 to Day 192 or Day 365 to Day 375; Day 182 to Day 224 or Day 365 to Day 407 ] [ Designated as safety issue: No ]
• Seroconversion rate [ Time Frame: Day 182 to Day 224 or from Day 365 to Day 407 ] [ Designated as safety issue: No ]
• Antibody GMT and proportion of subjects with antibody titer >specified cut-off [ Time Frame: Days 0, 182, 192 (if provided vaccine on Day 182), 224 (if provided vaccine on Day 182), 365, 375 (if provided vaccine on Day 365), 407 (if provided vaccine on Day 365), and 548 ] [ Designated as safety issue: No ]
• The antibody GMT and proportion of subjects with antibody titer > specified cut-off. [ Time Frame: Days 0, 10, 42, 182, 365, and 375 ] [ Designated as safety issue: No ]
• Seroconversion rate [ Time Frame: Days 0 to 10 and Days 0 to 42 ] [ Designated as safety issue: No ]

The purpose of this study is to determine whether GSK's avian flu vaccine GSK 1557484A is immunogenic when given to adults aged >=18 years.

All subjects will receive 3 doses of study vaccine, including 2 doses of active vaccine and 1 dose of placebo. All subjects will attend formal study center visits for safety and immunogenicity assessments on Days 0, 10, 42, 182, 192, 224, 365, 375, 407, and 548.

• Biological: Placebo
• Biological: GSK influenza virus vaccine 1557484A

Inclusion Criteria:

• A male or female 18 years of age or older at the time of the first vaccination.
• Written informed consent obtained from the subject.
• Stable health status as defined by absence of a health event satisfying the definition of a serious adverse event, or a change in an ongoing drug therapy due to therapeutic failure or symptoms of drug toxicity, within 1 month prior to enrollment.
• Access to a consistent means of telephone contact, which may be either in the home or at the workplace, land line or mobile, but NOT a pay phone or other multiple-user device.
• Comprehension of the study requirements, expressed availability for the required study period, and ability to attend scheduled visits.
• Subjects who the investigator believes can and will comply with the requirements of the protocol

Exclusion Criteria:

• Presence of evidence of substance abuse or of neurological or psychiatric diagnoses which, even if clinically stable, are deemed by the investigator to render the potential subject unable/unlikely to provide accurate safety reports.

• Diagnosed with cancer, or treatment for cancer, within 3 years.

  • Persons with a history of cancer who are disease-free without treatment for 3 years or more are eligible.
  • Persons with a history of histologically-confirmed basal cell carcinoma of the skin successfully treated with local excision only are excepted and may enroll within 3 years of diagnosis, but other histologic types of skin cancer require a 3 year untreated and disease-free window as above.
  • Women who are disease-free 3 years or more after treatment for breast cancer and receiving long-term prophylactic tamoxifen are excepted and may enroll.
• Presence of an oral temperature ≥ 37.8ºC, or acute symptoms greater than "mild" severity on the scheduled date of first vaccination.
• Any confirmed or suspected immunosuppressive or immunodeficient condition including history of human immunodeficiency virus (HIV) infection.
• Receipt of systemic glucocorticoids (prednisone >= 10 mg/day for more than 14 consecutive days) within 1 month prior to study enrollment, or any other cytotoxic or immunosuppressive drug within 6 months of study enrollment.
• Any significant disorder of coagulation or treatment with Coumadin derivatives or heparin.
• Administration of any vaccines within 30 days before the first study vaccine dose.
• Previous administration of any H5N1 vaccine.
• Use of any investigational or non-registered product (drug or vaccine) or planned participation in another investigational study within 30 days prior to study enrollment, or during the 18 months following the first test article dose. Use of any investigational or non-registered product with immunosuppressive properties is exclusionary at any time during the trial.
• Receipt of any immunoglobulins and/or any blood products within 6 months of study enrollment or planned administration of any of these products during the study period.
• Any known or suspected allergy to any constituent of influenza vaccines (including egg proteins or mercurial preservatives); a history of anaphylactic-type reaction to consumption of eggs; or a history of severe adverse reaction to a previous influenza vaccine.
• Known pregnancy or a positive urine beta-human chorionic gonadotropin (β-hCG) test result prior to vaccination.
• Lactating or nursing.
• Women of child bearing potential who lack a history of reliable contraceptive practices. The provision of this history does NOT replace the requirement to perform, and obtain negative results in pregnancy urine tests prior to treatments.
• Known receipt of analgesic or antipyretic medication with the specific intent of prophylaxis of vaccine reactogenicity on the day of first or any treatment. Subjects on stable chronic regimens of potentially analgesic or anti-pyretic medications for pre-existing diagnoses are not required to discontinue them (to do so would represent evaluation of combined vaccine reactogenicity AND treatment withdrawal - which is not the intent of the protocol).