Immune Response of Healthy Subjects Who Received Neonatal Vaccination Course With Engerix™-B Vaccine.

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 who received the complete neonatal primary vaccination course of Engerix™-B in the 103860/273 primary study approximately 20 years earlier. * Anti-HBs antibody concentrations less than the specified value at the last available follow-up time-point. * 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 vaccination. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine within 30 days preceding the Engerix™-B challenge dose, or planned use during the study period. * Chronic administration (defined as more than 14 days) of immunosuppressant or other immune-modifying drugs within six months prior to challenge dose administration. * Planned administration/ administration of a vaccine not foreseen by the study protocol starting from 30 days before the challenge dose and ending 30 days after. * Administration of a hepatitis B vaccine outside the context of this study between the follow-up time-point at which anti-HBs antibody concentrations was less than the specified value 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. * Acute disease at the time of enrolment. * Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection. * 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 challenge dose visit or planned administration during the study period. * Pregnant or lactating female. * Female planning to become pregnant or planning to discontinue contraceptive precautions.