Five-year Antibody Persistence and Safety Following a Booster Dose of Combined Haemophilus Influenzae Type B–neisseria Meningitidis Serogroup C–Tetanus Toxoid Conjugate Vaccine

Background: Booster vaccination with the combined Haemophilus influenza type b-Neisseria meningitides serogroup C-tetanus toxoid vaccine (Hib-MenC-TT) has been reported to induce different MenC antibody responses depending on the priming vaccines, with a possible impact on long-term protection. Here, the five-year persistence of immune responses induced by a booster dose of Hib-MenC-TT was evaluated in toddlers primed with either Hib-MenC-TT or MenC-TT.Methods: This is the follow-up of a phase III, open, randomized study, in which a Hib-MenC-TT booster dose was given at 13-14 months of age to toddlers primed with either 3 doses of Hib-MenC-TT or 2 doses of MenC-TT in infancy. Children in the control group had received 3 primary doses and a booster dose of MenC-CRM197. Functional antibodies against MenC were measured by a serum bactericidal assay with rabbit complement (rSBA-MenC) and antibodies against Hib polyribosylribitol phosphate by enzyme-linked immunosorbent assay. Serious adverse events considered by the investigator to be possibly related to vaccination were to be reported throughout the study.Results: At 66 months postbooster, rSBA-MenC titers >= 8 were retained by 82.6% of children primed with Hib-MenC-TT, 94.1% of children primed with MenC-TT, and 60.9% of children in the control group. All children who received the Hib-MenC-TT booster dose retained anti-polyribosylribitol phosphate concentrations >= 0.15 mu g/mL. No serious adverse events considered possibly related to vaccination were reported.Conclusions: There is evidence of good antibody persistence against MenC and Hib for more than five years postbooster vaccination with Hib-MenC-TT in toddlers primed with Hib-MenC-TT or MenC-TT.