To evaluate the safety, immune-response and efficacy of GSK Biologicals' EBV vaccine in a population at risk of developing infectious mononucleosis. Each subject will receive three doses of vaccine or placebo during the study period.

Inclusion Criteria:

• Healthy adolescent/adult subjects between and including 16 and 25 years of age at the time of screening.

  • Written informed consent obtained from the subject prior to enrolment.
  • Seronegative for EBV antibody.

Exclusion Criteria:

• Administration of immunoglobulin and/or any blood products within the three months (90 days) preceding the first dose of study vaccine or planned administration during the study period.

  • Use of any investigational or non-registered drug or vaccine other than the study vaccine within 30 days preceding the first dose of study vaccine, or planned use during the study period.
  • Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection.
  • Family history of congenital or hereditary immunodeficiency.
  • Major congenital defects or serious chronic illness.
  • History of any neurologic disorders or seizures, with the exception of a single febrile seizure during childhood.
  • Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or laboratory screening tests.
  • History of intravenous drug abuse within the past 2 years.
  • Known or suspected allergy to any vaccine component.