Inclusion Criteria:

• Subjects who the investigator believes that they can and will comply with the requirements of the protocol should be enrolled in the study.
• A male or female adult who received the complete neonatal primary vaccination course of hepatitis B vaccine (Engerix™-B), in the 103860/272 primary study approximately 20 years earlier.
• Documented level of anti-HBs antibody concentrations < 100mIU/ml at the previous long-term time-point for which serological results are available for that subject.
• Written informed consent obtained from the subject.
• Healthy subjects as established by medical history and clinical examination before entering into the study.
• If the subject is female, she must be of non-childbearing potential or if she is of childbearing potential, she must practice adequate contraception for 30 days prior to vaccination, have a negative pregnancy test and continue such precautions for 2 months after completion of the hepatitis B challenge dose.

Exclusion Criteria:

• Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned use during the study period.
• Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the hepatitis B vaccine challenge dose.
• Planned administration/ administration of a vaccine not foreseen by the study protocol during the period starting from 30 days before the hepatitis B vaccine challenge dose and ending 30 days after.
• Subjects who received a booster dose of hepatitis B vaccine outside the context of this study between the long-term time-point at the documented level of anti-HBs antibody concentrations and the current challenge dose study visit.
• Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product.
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection.
• Acute disease at the time of enrolment.
• Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or laboratory screening tests.
• Administration of immunoglobulins and/or any blood products within the three months preceding the hepatitis B vaccine challenge dose or planned administration during the study period.
• Pregnant or lactating female.
• Female planning to become pregnant or planning to discontinue contraceptive precautions.