Antibody Persistence After a Primary Series of a New DTaP-IPV-Hep B- PRP-T Combined Vaccine or Separate DTaP-IPV//PRP-T and Hepatitis B Vaccines at 2, 4, and 6 Months of Age and the Effect of a Subsequent DTaP-IPV//PRP-T Booster Vaccination at 18 Months of Age in Healthy Argentinean Infants

Objective: To assess antibody persistence after vaccination with a new, fully liquid, hexavalent DTaP-IPV-Hep B-PRP-T vaccine at 18 months of age versus licensed DTaP-IPV//PRP-T and hepatitis B (Hep B) vaccines, and to assess the immunogenicity and safety of a subsequent DTaP-IPV//PRP-T booster. Methods: A phase III, open-label, single-center study was conducted. Infants previously primed with 3 doses of DTaP-IPV-Hep B-PRP-T (Hexaxim: N = 232 [group 1]) or DTaP-IPV//PRP-T and hepatitis B vaccine (Pentaxim + Engerix B Pediatrico: N = 226 [group 2]) at 2, 4, and 6 months of age received a DTaP-IPV//PRP-T booster at 18 months of age. Antibodies were measured before and 1 month after booster vaccination. Safety was evaluated from parental reports. Analyses were descriptive. Results: Antibody persistence was high and similar in each group for each antigen except for Hep B, for which the percentage (95% confidence interval) of participants with a titer of >= 10 mIU/mL was higher in group 2 (99.5% [97.5%, 100.0%]) than in group 1 (85.5% [80.3%, 89.8% ]). Postbooster seroprotection (diphtheria, tetanus, inactivated poliovirus, polyribosyl-ribitol phosphate) and serconversion (pertussis toxoid, filamentous hemagglutinin) rates were high and similar in each group, and geometric mean antibody concentrations increased markedly in both groups. Safety after the booster vaccination was good and independent of the primary-series vaccine, although one serious adverse event of convulsions was considered to be vaccine related. Conclusions: The DTaP-IPV/PRP-T booster vaccination at 18 months of age was similarly immunogenic and well tolerated after primary-series vaccination with either the investigational hexavalent vaccine or the reference pentavalent vaccine. This confirms the suitability of a booster vaccination of DTaP-IPV//PRP-T after a primary series of the new DTaP-IPV-Hep B-PRP-T vaccine.