Randomized, open-label study of the impact of age on booster responses to the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine in children in India

In this phase III, open-label, multicenter, and descriptive study in India, children primed with 3 doses (at ages 6, 10, and 14 weeks) of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) were randomized (1:1) to receive a booster dose at 9 to 12 (early booster) or 15 to 18 months old (late booster) in order to evaluate impact of age at booster. We also evaluated a 2-dose catch-up vaccination plus an experimental booster dose in unprimed children age 12 to 18 months. The early booster, late booster, and catch-up vaccinations were administered to 74, 95, and 87 children, respectively; 66, 71, and 81 children, respectively, were included in the immunogenicity according-to-protocol cohort. One month postbooster, for each PHiD-CV serotype, ≥95.2% (early booster) and ≥93.8% (late booster) of the children had antibody concentrations of ≥0.2 μg/ml; ≥96.7% and ≥93.0%, respectively, had opsonophagocytic activity (OPA) titers of ≥8. The postbooster antibody geometric mean concentrations (GMCs) were in similar ranges for early and late boosters; the OPA titers appeared to be lower for most PHiD-CV serotypes (except 6B and 19F) after the early booster. After dose 2 and postbooster, for each PHiD-CV serotype, ≥88.6% and ≥96.3%, respectively, of the catch-up immunogenicity according-to-protocol cohort had antibody concentrations of ≥0.2 μg/ml; ≥71.4% and ≥90.6%, respectively, had OPA titers of ≥8. At least 1 serious adverse event was reported by 2 children in the early booster (skin infection and gastroenteritis) and 1 child in the catch-up group (febrile convulsion and urinary tract infection); all were resolved, and none were considered by the investigators to be vaccine related. PHiD-CV induced robust immune responses regardless of age at booster. Booster vaccination following 2 catch-up doses induced robust immune responses indicative of effective priming and immunological memory. (These studies have been registered at www.clinicaltrials.gov under registration no. NCT01030822 and NCT00814710; a protocol summary is available at www.gsk-clinicalstudyregister.com [study ID 112909]).