The B-cell response to a primary and booster course of MenACWY-CRM197vaccine administered at 2, 4 and 12 months of age

A quadrivalent meningococcal vaccine conjugated to CRM197(MenACWY-CRM197) is immunogenic in young infants. We assessed the memory B-cell and antibody responses after a primary and booster course of MenACWY-CRM197in children. At 5 months of age, following primary immunisation, serogroup-specific memory B-cells were detectable in fewer than 25% of children, although protective antibody titres (hSBA>=4) were detectable in 69% of children against serogroup A and more than 95% against the other serogroups. At 12 months, before booster immunisation the percentages with hSBA>=4 were 5% for serogroup A, and between 44 and 70% for the other serogroups. One month after booster immunisation with MenACWY-CRM197over 50% of children had detectable memory B-cells, and 91% had hSBA>=4 against serogroup A and more than 99% against the other serogroups. These data show that few antigen-specific anticapsular memory B-cells can be detected after two-doses priming with MenACWY-CRM197. For MenC and CRM197, the antigens with the highest number of B-cells at 5 months, there was a definite (p