Immune Response & Safety of GSK Biologicals' Mencevax™ ACWY in Subjects Primed in the DTPW-HBV=HIB-MENAC-TT-011 Study

This study will be conducted in three stages. In the DTP booster stage at 15 to 24 months of age, all subjects will receive a booster dose of Tritanrix™-HepB/Hiberix™. In the Mencevax™ ACWY "full dose" stage at 24 to 30 months of age all subjects will receive a dose of Mencevax™ ACWY. In the Mencevax™ ACWY "small dose" stage at 30 to 36 months of age, the first 75 subjects in each of the two centers will be tested for boostability of the MenA and MenC immune response by giving a fifth of a dose of a Mencevax™ ACWY vaccine. The Protocol Posting has been updated in order to comply with the FDA Amendment Act, Sep 2007.

Subjects in the group that was previously primed with Tritanrix™-HepB/Hiberix™ will be the control group for the group that was previously primed with Tritanrix™-HepB/Hib-MenAC.

Blood samples will be drawn from subjects as follows:

* prior to and one month after the full dose of the Mencevax™ ACWY vaccine.
* prior to and one month after 1/5th of a dose of Mencevax™ ACWY vaccine (only for the first 75 subjects in each of the two centers).

Eligibility Criteria:
Inclusion criteria:

* Subjects who the investigator believes that their parents/guardians can and will comply with the requirements of the protocol.
* A male or female between, and including, 15 and 24 months of age at the time of vaccination.
* Written informed consent obtained from the parent or guardian of the subject.
* Healthy subjects as established by medical history and clinical examination before entering into the study.
* Having participated in the primary vaccination study DTPW-HBV=HIB-MENAC-TT-011 (eTrack No. 100478) in Center No. 4328 or Center No.4329.

Exclusion criteria:

* Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine within 30 days preceding the vaccination, 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 vaccination.
* Planned administration/ administration of a vaccine not foreseen by the study protocol within 30 days of vaccination; with the exception of oral poliovirus vaccine (OPV).
* Booster vaccination against diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b (Hib) and/or meningococcal serogroups A and/or C disease, after the date of the study conclusion visit of the primary vaccination study DTPW-HBV=HIB-MENAC-TT-011 (eTrack No. 100478).
* History of diphtheria, tetanus, pertussis, hepatitis B, Hib and/or meningococcal serogroup A or C disease.
* Known exposure to diphtheria, tetanus, pertussis, hepatitis B, Hib and/or meningococcal serogroup A or C disease.
* Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination.
* A family history of congenital or hereditary immunodeficiency.
* History of allergic disease or reactions likely to be exacerbated by any component of the vaccine.
* Major congenital defects or serious chronic illness.
* History of any neurologic disorders or seizures including febrile seizures in infancy.
* Acute disease at the time of enrolment.
* Planned or actual administration of immunoglobulins and/or any blood products within the three months preceding Mencevax™ ACWY vaccination.