Immunization with 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) according to different schedules in infants in South Africa: a phase III trial.

Background: Limited clinical data exists to assess differences between various infant pneumococcal conjugate vaccine schedules. In this trial, we evaluated immunogenicity of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) administered using 3 different immunization schedules in HIV unexposed-uninfected infants in South Africa.

Methods: In this phase III, open, single-center, controlled study (clinicaltrials.gov: NCT00829010), 300 infants were randomized (1:1:1) to 1 of 3 PHiD-CV schedules: 3-dose priming and booster (3 + 1); 3-dose priming without booster (3 + 0); or 2-dose priming and booster (2 + 1). The booster was administered at 9-10 months of age. immune responses were assessed up to 21 months after primary vaccination.

Results: Post-priming antibody levels tended to be lower in the 2 + 1 group. At 6 months post-priming, antibody concentrations and opsonophagocytic activity titers were within similar ranges after 2- or 3-dose priming. Robust increases were observed pre- to post-booster in the 3 + 1 and 2 + 1 groups.

Conclusions: PHiD-CV was immunogenic when administered in different schedules. Post-booster responses suggest effective immunological priming with both 2- and 3-dose primary series and support administration of the booster dose at 9-10 months of age.