Background: We have previously shown that primary vaccination with 2 formulations of an investigational pneumococcal vaccine containing each of the highly conserved pneumococcal proteins pneumolysin toxoid (dPly) and histidine-triad protein D (PhtD) at either 10µg (PHiD-CV/dPly/PhtD-10) or 30µg (PHiD-CV/dPly/PhtD-30) combined with polysaccharide conjugates of 10-valent pneumococcal conjugate vaccine (PHiD-CV, GSK Vaccines [not licensed in USA]) induced robust immune responses in infants in Europe. Here, we present immunogenicity results following administration of a booster dose of these 2 vaccine formulations in the same study.
Methods: In this phase II, multicenter, observer-blind trial (NCT01204658) in Europe, 576 infants aged 614 weeks were randomized 1:1:1:1 to receive primary and booster vaccinations (at ages 2, 3, 4 and 1215 months) with either PHiD-CV/dPly/PhtD-10, PHiD-CV/dPly/PhtD-30, PHiD-CV or 13-valent pneumococcal conjugate vaccine (PCV13, Pfizer), co-administered with DTPa-HBV-IPV/Hib. Immune responses were assessed pre- and 1 month post-booster.
Results: All vaccinees had post-booster anti-Ply and anti-PhtD antibody concentrations ≥ assay cut-off (12 and 17 EL.U/mL, respectively), except for PhtD in PHiD-CV vaccinees: 96.1% of toddlers. Increases in geometric mean antibody concentrations (GMCs) from pre- to post-booster timepoint were observed (table 1). For each of the 10 common vaccine pneumococcal serotypes, ≥96.9% of toddlers had post-booster antibody concentrations ≥0.2 μg/mL; GMCs are shown in table 1. Pneumococcal opsonophagocytic activity (OPA) seemed to be similar between PHiD-CV/dPly/PhtD-10, PHiD-CV/dPly/PhtD-30 and PHiD-CV recipients (except for 9V geometric mean OPA titers in PHiD-CV/dPly/PhtD-10 versus PHiD-CV group) (table 2). Post-booster anti-protein D GMCs tended to be lower in the protein-based formulations groups than in the PHiD-CV group (table 1).
Conclusion: PHiD-CV/dPly/PhtD-10 and PHiD-CV/dPly/PhtD-30 induced booster responses to Ply and PhtD. No interference with immune responses to pneumococcal conjugates was observed when combining dPly and PhtD with the 10 PHiD-CV polysaccharide conjugates.
Funding: GlaxoSmithKline Biologicals SA
S. A. Silfverdal, GSK: Investigator , The study was financed by GSK to institution and no personal fee or honoraria was given
J. Wysocki, GSK: Grant Investigator , investigator fee
P. Albrecht, GSK: Investigator , Research support
Pfizer: Grant Investigator , Educational grant and Research support
M. Traskine, GSK: Employee , Salary
A. Gardev, GSK: formerly employed by GSK , Salary at the time of GSK employment
Y. Song, GSK: Consultant , Consulting fee
D. Borys, GSK Biologicals: Employee and Shareholder , I have share options/shares of GSK Biologicals and Salary