Antibody levels have been measured at 18 months after the administration of a booster dose of Menitorix at age 14 Months to subjects who had been primed in infancy with either Menitorix at 2, 4 and 6 months of age or with NeisVac-C at 2, 4 months of age (and a DTPa/ Hib containing vaccine at 2, 4, 6 months of age).