Can two different pneumococcal conjugate vaccines be used to complete the infant vaccination series? A randomized trial exploring interchangeability of the 13-valent pneumococcal conjugate vaccine and the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine.

Background: We assessed the safety and immunogenicity of 2 + 1 infant regimens initiated with the 13-valent pneumococcal conjugate vaccine (PCV13) and completed with the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV). Methods: This partially blinded study randomized 6-12-week-old infants to receive two-dose priming and a booster (at ages 2, 4, 12-15 months) with: PCV13 at priming and PHiD-CV at boosting (PPS); PCV13 then PHiD-CV at priming and PHiD-CV at boosting (PSS); or PHiD-CV at priming and boosting (SSS control). All analyses were descriptive, i.e., no statistical significance tests were done. Results: The total vaccinated cohort at priming comprised 294 infants. Grade 3 adverse events were reported after 8.7% (PPS), 11.4% (PSS), and 16.9% (SSS) of primary doses (primary objective). No serious adverse events were considered vaccination-related. For most PHiD-CV serotypes, observed percentages of children reaching antibody concentrations ≥0.2 µg/mL and opsonophagocytic activity (OPA) titers above cutoffs were similar across groups 1 month post-priming and post-booster. Observed geometric mean antibody concentrations and OPA titers were lower for some PHiD-CV serotypes with the mixed regimens than with PHiD-CV only, especially for PSS. However, no tests of statistical significance were performed. Conclusions: Immunogenicity of the two mixed PCV13/PHiD-CV regimens seemed mostly similar to that of a PHiD-CV-only series, although observed antibody GMCs and OPA GMTs for some PHiD-CV serotypes were lower. No safety concerns were raised. The clinical relevance of the observed differences is unknown. Clinical trial registration: ClinicalTrials.gov: NCT01641133.