Long-term Persistence of Immunity to Hepatitis B in Adults Vaccinated With GlaxoSmithKline (GSK) Biologicals' Hepatitis B Vaccine (HBV), Engerix-B

Inclusion Criteria: * Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol. * A male or female between and including 40 and 60 years of age (from and including the 40th birthday up to, but excluding, the 61st birthday) at the time of the vaccination. * Written informed consent obtained from the subject. * Documented evidence of previous vaccination with three or four consecutive doses of Engerix-B administered in adulthood (i.e. at least 18 years of age) with * the last dose received 4 to 12 months after the previous one, * no subsequent booster dose ever received later, and * the last dose received 20 to 30 years before enrolment. * Female subjects of non-childbearing potential may be enrolled in the study. * Non-childbearing potential is defined as pre-menarche, hysterectomy, ovariectomy or post-menopause. * Female subjects of childbearing potential may be enrolled in the study, if the subject: * has practiced adequate contraception for 30 days prior to vaccination, and * has a negative pregnancy test on the day of vaccination, and * has agreed to continue adequate contraception during the entire treatment period and for one month after vaccination. Exclusion Criteria: * Use of any investigational or non-registered product other than the study vaccine during the period starting 30 days before the dose of study vaccine, or planned use during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the vaccine dose. For corticosteroids, this will mean prednisone ≥ 20 mg/day, or equivalent. Inhaled and topical steroids are allowed. * Administration of long-acting immune-modifying drugs at any time during the study period. * Previous hepatitis B booster vaccination since completion of the primary vaccination series with three or four doses of Engerix-B. * Planned administration of a vaccine not foreseen by the study protocol within 30 days preceding the dose of study vaccine, or planned administration during the study period, with the exception of seasonal influenza vaccine. * Any medical condition that in the judgment of the investigator places the subject at undue risk by participating in the study. * 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 vaccine/product. * History of hepatitis B disease or episode of jaundice with unknown etiology. * History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine. * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination. * Major congenital defects or serious chronic illness (including insulin-dependent diabetes). * Acute disease and/or fever at the time of enrolment. * Fever is defined as temperature ≥37.5°C for oral, axillary or tympanic route, or 38.0°C on rectal route. * Subjects with a minor illness without fever may be enrolled at the discretion of the investigator. * Administration of immunoglobulins and/or any blood products during the period starting 3 months before the dose of study vaccine, or planned administration during the study period. * Drug and/ or alcohol abuse within the last 5 years.