Safety and immunogenicity of CRM197-conjugated pneumococcal-meningococcal C combination vaccine (9vPnC-MnCC) whether given in two or three primary doses.

This randomized trial compares safety and immunogenicity when vaccinating infants with a pneumococcal-meningococcal conjugate vaccine in two doses vs. three doses. Infants (N=223) received 9vPnC-MnCC (CRM197-conjugated pneumococcal serotypes 1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F and meningococcal C polysaccharides) either at 3 and 5 or 3, 4 and 5 months and a booster with either 9vPnC-MnCC or 23-valent pneumococcal-polysaccharide vaccine (23vPPS) and CRM197-MnCC, at 12 months. Safety was monitored and IgG measured at 3, 6, 12 and 13 months in all subjects and serum bactericidal activity (SBA) in half. The 9vPnC-MnCC vaccine was safe and induced significant IgG to all components. Three doses induced higher antibody GMCs (geometric mean concentrations) at 6 months to seven of nine pneumococcal serotypes. This was most significant for 6B and 23F (p<0.001), that also showed lower rate of responders>0.35 (6B, 23F) and >0.5 microg/mL (6B). Antibody GMCs remained lower following 9vPnC-MnCC booster in subjects primed with two doses although only significant for serotype 18C. Significant memory responses were observed 1 week after the 23vPPS toddler dose. MnCC-IgG GMC was lower after two doses, however with comparable SBA. This study shows that the 9vPnC-MnCC vaccine is safe and induces successful immunological memory, whether given in two or three primary doses.