Response to GSK Biologicals' Tritanrix-HepB/Hib-MenAC Vacc (4th Dose) at 15-24m & Mencevax ACWY at 24-30m

Assess Immunogenicity, Safety & Reactogenicity of a 4th Dose of GSK Biologicals' Tritanrix-HepB/Hib-MenAC at 15-24 m & of a Dose of Mencevax ACWY at 24-30 m in Subjects Primed With 3 Doses of Tritanrix-HepB/Hib-MenAC

The purpose of the study is to evaluate the immunogenicity, safety and reactogenicity of a booster dose of DTPw-HBV/Hib-MenAC compared to DTPw-HBV/Hib given to healthy subjects at 15 to 24 months of age primed with 3 doses of Tritanrix-HepB/Hib-MenAC in study 100480. Antibody persistence will be evaluated at 24 to 30 months. Immunogenicity, safety and reactogenicity of a dose of Mencevax ACWY given at 24 to 30 months will also be evaluated when given to subjects not boosted with a MenA conjugate and/or MenC containing vaccine.

This study will be conducted in two stages. In the DTP booster phase subjects will receive a booster dose of Tritanrix-HepB/Hib-MenAC or Tritanrix-HepB/Hib (active control) at 15 to 24 months in a single-blind manner so that the subjects' parents will not know which vaccine was administered to their child (this booster phase is no longer recruiting). In the Mencevax ACWY phase at 24-30 months a dose of Mencevax ACWY will be given to subjects who were not boosted with a MenA conjugate and/or MenC containing vaccine at 15-24 months in an open manner (this booster phase is not yet recruiting). Up to four blood samples will be taken: before and one month after the administration of the DTP booster dose and of Mencevax ACWY. To comply with the immunisation calender of Thailand, at 15-24 months all subjects will receive OPV. At 16-25 months 2 doses of Japanese Encephalitis (JE) vaccine or a dose of varicella vaccine will be offered and at 25-31 months a dose of varicella or JE vaccine will be offered.

Inclusion criteria:

• Healthy male or female between and including 15 and 24 months of age
• Having participated in the primary vaccination study DTPW-HBV=HIB-MENAC-TT-003 (eTrack No. 100480)

Exclusion criteria:

• Booster vaccination against diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b (Hib) and/or meningococcal serogroups A and/or C disease not foreseen in the protocol, after the date of the study conclusion visit of the primary vaccination study DTPW-HBV=HIB-MENAC-TT-003 (eTrack No. 100480).
• History of or 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.
• A family history of congenital or hereditary immunodeficiency.
• Major congenital defects or serious chronic illness.
• History of any neurologic disorders or seizures including febrile seizures (at least two events) in infancy.