Immunogenicity and Safety of GlaxoSmithKline (GSK) Biologicals' Boostrix™ Vaccine in Previously Boosted Young Adults

Inclusion Criteria: * Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g. completion of the diary cards, return for follow-up visit). * Subjects who have received a dose of Tdap or Td vaccines 10 years (+/-300 days) back, in study NCT00109330. * Written informed consent obtained from the subject. * Healthy subjects as established by medical history and clinical examination before entering into the study. * Female subjects of non-childbearing potential may be enrolled in the study. * Non-childbearing potential is defined as pre-menarche, current tubal ligation, 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 1 month after completion of the vaccine dose. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine within 30 days preceding the dose of study vaccine, or planned use during the study period. * Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immune-modifying drugs within six months prior to the booster vaccine dose . For corticosteroids, this will mean prednisone (≥ 20 mg/day (for adult subjects), or equivalent. Inhaled and topical steroids are allowed. * Planned administration/administration of a vaccine not foreseen by the study protocol in the period starting 30 days before and ending 31 days after the dose of vaccine, with the exception of Influenza vaccine which is allowed throughout the study period. * 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 (pharmaceutical product or device). * Previous vaccination against diphtheria, tetanus or pertussis since the last dose received in the Study NCT00109330. * History of diphtheria, tetanus or pertussis diseases following the receipt of booster dose in the Study NCT00109330. * Severe allergic reaction (e.g. anaphylaxis) after previous administration of any tetanus toxoid, diphtheria toxoid, or pertussis-antigen containing vaccines, or any component of Boostrix. * Hypersensitivity to latex. * Encephalopathy (e.g. coma, decreased level of consciousness, prolonged seizures) of unknown etiology occurring within 7 days following previous vaccination with pertussis-containing vaccine. * History of any neurological disorders or seizures. * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required). * Acute disease and/or fever at the time of enrolment. * Fever is defined as temperature ≥ 99.5°F for oral, axillary or tympanic route, or ≥ 100.4°F for rectal route. The preferred route for recording temperature in this study will be oral. * Subjects with a minor illness (such as mild diarrhea, mild upper respiratory infection) without fever may, be enrolled at the discretion of the investigator. * Administration of immunoglobulins and/or any blood products within the 3 months preceding the booster dose of study vaccine or planned administration during the study period. * Pregnant or lactating female. * Female planning to become pregnant or planning to discontinue contraceptive precautions up to 1 month post-vaccination.