The study will enrol subjects of 12 to 14 months of age and subjects of 3 to 5 years of age. Meningitec™ or Mencevax™ ACWY vaccine will serve as active control. The study will be conducted in two stages: The primary vaccination phase (Study Stage 1) of the study will include all subjects; the second (booster/persistence) phase of the study (Study Stage 2) will include subjects in the active control groups and in the group which was primed with the selected MenACWY formulation.