INTRODUCTION: Vaccination with formulations containing pneumococcal protein antigens such as pneumolysin toxoid (dPly) and histidine-triad protein D (PhtD) may extend serotype-related protection of pneumococcal conjugate vaccines (PCVs) against Streptococcus pneumoniae. METHODS: This phase II, multi-center, observer-blind trial conducted in Europe (NCT01204658) assessed 2 investigational vaccines containing 10 serotype-specific polysaccharide conjugates of PHiD-CV and either 10 or 30µg of dPly and PhtD each. Infants randomized 1:1:1:1 received 4 doses of PHiD-CV/dPly/PhtD-10, PHiD-CV/dPly/PhtD-30, PHiD-CV, or 13-valent PCV (PCV13), co-administered with DTPa-HBV-IPV/Hib, at ages ∼2, 3, 4 and 12-15months. Occurrences of fever >40.0°C following primary vaccination with PHiD-CV/dPly/PhtD vaccines compared to PHiD-CV (non-inferiority objective), dose superiority, safety and immunogenicity were assessed. RESULTS: 575 children received primary vaccination, and 564 booster vaccination. The non-inferiority objective was met; no fever >40.0°C causally related to vaccination was reported during primary vaccination. Incidence of adverse events appeared similar between the 3 PHiD-CV groups. Serious adverse events were reported in 13, 9, 21 (1 related to vaccination), and 17 children in the PHiD-CV/dPly/PhtD-10, PHiD-CV/dPly/PhtD-30, PHiD-CV, and PCV13 groups, respectively. PHiD-CV/dPly/PhtD-30 was superior to PHiD-CV/dPly/PhtD-10 in terms of post-dose 3 anti-Ply and Anti-PhtD antibody levels. Anti-Ply and anti-PhtD antibody levels were higher in both PHiD-CV/dPly/PhtD groups than in controls and increased from post-primary to post-booster timepoint. Post-primary and booster vaccination, for each PHiD-CV serotype, ≥98.5% of participants in PHiD-CV/dPly/PhtD groups had antibody concentrations ≥ 0.2μg/mL, except for 6B (≥72.3%) and 23F (≥82.7%) post-primary vaccination. Similar results were observed in the PHiD-CV group. Immune responses to protein D and DTPa-HBV-IPV/Hib were within similar ranges for the 3 PHiD-CV groups. CONCLUSION: Both PHiD-CV/dPly/PhtD formulations co-administered with DTPa-HBV-IPV/Hib in infants were well-tolerated and immunogenic for dPly and PhtD antigens, while immune responses to serotype-specific, protein D and co-administered antigens did not appear altered in comparison to PHiD-CV group.

Clinical Sciences Pediatrics Umeå University SE 90185 Umeå Sweden

Department and Clinic of Pediatric Infectious Diseases Wroclaw Medical University 2 2A Chalubinskiego 50 368 Wroclaw Poland

Department of Social Medicine Faculty of Medicine in Hradec Králové Charles University Prague Šimkova 870 500 38 Hradec Králové Czech Republic

GSK Av Fleming 20 1300 Wavre Belgium

Medical University of Warsaw Department of Paediatric Gastroenterology and Nutrition ul Żwirki i Wigury 63A 02 091 Warsaw Poland

Poznań University of Medical Sciences ul H Święcickiego 6 60 781 Poznań Poland; Regional Medical Center for Mother and Child ul Smoluchowskiego 11 60 179 Poznań Poland

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