Protective immune responses against Haemophilus influenza type b elicited by a fully-liquid DTaP-IPV-Hib-HepB vaccine (VAXELIS™).

BACKGROUND: DTaP-IPV-Hib-HepB is a fully-liquid, hexavalent combination vaccine (Vaxelis™) approved for vaccination against diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, and invasive disease due to Haemophilus influenzae type b (Hib). Hib capsular polysaccharide, polyribosylribitol phosphate (PRP), is conjugated to Neisseria meningitidis outer membrane protein complex (OMPC). Safety and immunogenicity of DTaP-IPV-Hib-HepB were evaluated in 6 Phase III clinical studies including > 5,200 children. Studies included vaccination schedules in the United States (2, 4, 6 months of age) and Europe (2, 3, 4, 12 months of age and 2,4,11-12 months of age). METHODS: Data pertaining to anti-PRP responses of DTaP-IPV-Hib-Hep B compared to control vaccines from 5 Phase III studies are summarized. RESULTS: Post-infant series, the percentage of participants that achieved protective antibody thresholds for PRP (anti-PRP titer ≥ 0.15 µg/mL and ≥ 1.0 µg/mL, respectively) were higher in DTaP-IPV-Hib-HepB recipients compared to recipients who received control vaccines. A high level of protective responses (96.6% at ≥ 0.15 µg/mL [95% CI:94.8, 97.9%]; 72.9% at ≥ 1.0 µg/mL [95% CI:69.2,76.4%]) were seen post-dose 2 of the 2 + 1 vaccination schedule and met superiority criteria over comparator, p-value < 0.001. In the same schedule, prior to administration of the toddler dose (in the second year of life), anti-PRP titers were higher in DTaP-IPV-Hib-HepB recipients (91.4% at ≥ 0.15 µg/mL; 46.8% at ≥ 1.0 µg/mL) as compared to recipients who received control vaccines (63.4% at ≥ 0.15 µg/mL; 17.1% at ≥ 1.0 µg/mL). One-month post-toddler dose, high levels of anti-PRP titers were achieved in both DTaP-IPV-Hib-HepB recipients (99.8% at ≥ 0.15 µg/mL; 96.6% at ≥ 1.0 µg/mL) and recipients who received control vaccines (99.5% at ≥ 0.15 µg/mL; 94.9% at ≥ 1.0 µg/mL). CONCLUSIONS: These results support that DTaP-IPV-Hib-HepB induces a robust and sustained early Hib response. During the high-risk period for Hib disease after the infant vaccine and prior to the toddler dose; >90% of recipients maintained superior protective anti-PRP levels compared to control.