This study will assess the long-term protection offered by the new meningococcal vaccine 134612 compared to Meningitec™ up to 4 years after vaccination of toddlers. Subjects were previously vaccinated at 12 to 23 months of age with GSK Biologicals' meningococcal vaccine 134612 or Meningitec™. All subjects received at least one dose of Priorix-Tetra™. This extension phase starts 24 months after vaccination and the subjects who were vaccinated in the primary study will be enrolled in this extension study. No new subjects will be enrolled. The subjects will have a blood sample taken at 24, 36 and 48 months after primary vaccination.