Immune response and one-year antibody persistence after a fourth dose of a novel Haemophilus influenzae type b and Neisseria meningitidis serogroups C and Y-tetanus toxoid conjugate vaccine (HibMenCY) at 12 to 15 months of age.

A total of 236 infants received a fourth Haemophilus influenzae type b-Neisseria meningitidis serogroups C and Y-tetanus toxoid conjugate vaccine (HibMenCY) dose at 12 to 15 months. One month later, the proportion with anti-PRP antibody > or =1.0 microg/mL and bactericidal titers > or =1:8 to MenC and MenY was 98.9%, 96.9%, and 95.4%, respectively. One year later, anti-PRP concentrations > or =0.15 microg/mL, and MenC and MenY bactericidal titers > or =1:8 persisted in 100%, 96.6%, and 83.8%, respectively. The safety profile of HibMenCY was comparable to Hib.