Children 14 to 18 months of life, previously vaccinated with 2 doses of tetanus toxoid conjugated polysaccharide men C vaccine or three doses of the CRM197 conjugated polysaccharide men C vaccine before 7 months of age, are randomized to receive any of the two vaccines. Serum antibody activity against meningococcus C will be measured inmediately before and 4 weeks after the booster dose. Children will also be vaccinated with a combined vaccine containing DTaP+IPV+Hib.