• 1M post 4th dose of study vaccine & applicable control: SBA-MenC/A≥128, anti-PRP≥1. 1M post Mencevax booster in subjects primed with MenAC conjugate: SBA-MenC/A≥128.
  

• Pre and 1M post each vacc dose: antibody conc or titer, seroprot, seropos and/or vacc response to all antigens administered. Loc/gen symp: D 0-3, unsol symp: D 0-30 post each vac. SAE for entire study.
  

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.