Immunology of combining CRM197 conjugates for Streptococcus pneumoniae, Neisseria meningitis and Haemophilus influenzae in Chilean infants

We evaluated the immunogenicity and safety of an investigational combination of 9-valent pneumococcal conjugate vaccine (PCV9) and meningococcal group C conjugate (MnCC) vaccine (PCV9–MnCC) administered concomitantly with Haemophilus influenzae type b (Hib) conjugate vaccine, and of a combination of the three vaccines mixed together as a single injection (Hib-PCV9–MnCC), and compared them to separately administered PCV9 and MnCC dispensed to Chilean infants at 2, 4, and 6 months of age. The frequency of adverse events was similar among groups. Recipients of PCV9 alone or in combination with the other vaccines mounted significant antibody responses to the nine pneumococcal serotypes in PCV9, with >88% achieving protective levels of ≥0.35 μg/mL. For serotypes 6B, 9V, and 5, recipients of PCV9 alone had significantly higher geometric mean concentrations (GMCs) than those of the other vaccine groups. Similarly, the GMC of anti-PRP antibodies was significantly lower among recipients of Hib-PCV9–MnCC than among those who received Hib vaccine separately from PCV9 or MnCC. In Chilean infants, PCV9, PCV9–MnCC, and Hib-PCV9–MnCC were highly immunogenic and safe. Overall, interactions of PCV9, MnCC and Hib affected the magnitude (GMC) of the primary antibody responses to some of the antigens, but not the percentage of subjects who achieved protective antibody thresholds.