A randomised study comparing the safety and immunogenicity of a conjugate vaccine combination containing meningococcal group C and pneumococcal capsular polysaccharide - CRM197 with a meningococcal group C conjugate vaccine in healthy infants: challenge phase

Background: A combination nonavalent pneumococcal-group C meningococcal conjugate vaccine (Pnc9-MenC) was previously found to be safe and immunogenic when administered to infants at 2, 3 and 4 monts. This study describes the persistence of immunity at 12 months of age and the immunologic response to a challenge dose of either meningococcal polysaccharide vaccine (Meningivac A + C™; MnA + C), or MenC. Methods: A phase II, randomized, controlled trial of healthy infants. Subjects were given Pnc9-MenC or MenC vaccine at 2, 3 and 4 months of age and then challenged with either MenC of MnA + C. Group C meningococcal immonogenicity was measured by serum bactericidal assay (SBA) and an enzyme-linked immunosorbent assay (ELISA) adapted to measure antibody avidity pre- and post-challenge. Result: The MenC vaccine was more immunogenic than the Pnc9-MenC vaccine in persistence of serogroup C meningococcal polysaccharide antibodies at 12 months of age. Post-challenge at 13 months there were significant differences between the four groups in the induction of serogroup C meningococcal polysaccharide antibodies. The responses to MenC/MenC were significantly higher than in the other groups (p<0.001) and the responses to Pnc9-MenC/MnA + C were significantly lower than in the other groups ( p