Immunogenicity and Reactogenicity of a Booster Dose of a Novel Combined Haemophilus influenzae Type b-Neisseria meningitidis Serogroup C-Tetanus Toxoid Conjugate Vaccine Given to Toddlers of 13–14 Months of Age With Antibody Persistence Up to 31 Months of Age

BACKGROUND:A combined Haemophilus influenzae type b and Neisseria meningitidis serogroup C tetanus toxoid conjugate vaccine (Hib-MenC-TT) may be a convenient alternative to separate Hib and MenC conjugate vaccines. METHODS:Healthy infants randomized in a previous study for priming at 2, 4, and 6 monthsHib-MenC-TT primed group, 3 doses of Hib-MenC-TT + DTPa-HBV-IPV (N = 87); MenC-TT primed group, 2 doses of MenC-TT (NeisVac-C™; Baxter Healthcare SA, Zuürich, Switzerland) + 3 doses of DTPa/Hib containing vaccines (N = 178); MenC-CRM primed group, 3 doses of MenC-CRM197(Meningitec™; Wyeth Corporation Delaware, Madison, NJ) + DTPa-HBV-IPV/Hib (N = 93). At 13-14 months of age, Hib-MenC-TT and MenC-TT primed groups received a Hib-MenC-TT booster dose and the MenC-CRM primed group a booster dose of DTPa-HBV-IPV/Hib. Blood samples were taken before and at 1 and 18 months postbooster. RESULTS:Before the booster dose, persistence of anti-polyribosyl ribitol phosphate (PRP) antibody concentration ≥0.15 μg/mL in the Hib-MenC-TT (96.4%) and MenC-TT (96.1%) primed groups and of MenC bactericidal titers ≥1:8 in the Hib-MenC-TT primed group (96.3%) was statistically significantly higher than in the MenC-CRM primed group (86.4% and 85.4%, respectively). One month after the Hib-MenC-TT booster, 99.2% subjects in the Hib-MenC-TT primed + MenC-TT primed pooled groups had anti-PRP levels ≥1 μg/mL, and 99.6% had SBA-MenC titers ≥1:128. The Hib-MenC-TT booster tended to be less reactogenic than the DTPa-HBV-IPV/Hib control and no serious adverse events related to vaccination were reported. Eighteen months after boosting with Hib-MenC-TT, SBA-MenC titers ≥1:8 persisted in 92.7% subjects and anti-PRP ≥0.15 μg/mL persisted in 99.4%. CONCLUSIONS:Primary immunization with 3 doses of Hib-MenC-TT coadministered with DTPa-HBV-IPV induced antibodies that persisted up to the second year of life. The Hib-MenC-TT booster administered to primed toddlers induced robust and persistent antibody responses to both the Hib and MenC components and had an acceptable safety profile.