Comparison of antibody kinetics following meningococcal serogroup C conjugate vaccine between healthy adults previously vaccinated with meningococcal A/C polysaccharide vaccine and vaccine-naïve controls.

Few data are available on the kinetics of meningococcal serogroup C-specific antibody production following meningococcal serogroup C conjugate (MCC) vaccination, particularly in those who have received prior meningococcal A/C polysaccharide (MACP) vaccination(s). Laboratory staff who had previously received either one dose (n = 35), two doses (n = 18) of MACP vaccine or who were naïve to previous meningococcal vaccination (n = 42) were vaccinated with MCC. Bloods were taken pre-vaccination, on the subsequent 4 days and on days 10 and 28. Serogroup C serum bactericidal antibody (SBA), and anti-serogroup C-specific IgG, IgM and IgA were measured. There were no significant differences between the groups who had received either 2 or 1 prior dose(s) of MACP, therefore, these results were combined. Up to day 4 there was no evidence of a significant increase or decrease in the median levels of SBA, IgG, IgM or IgA in either the naïve or MACP groups, although about 20% of individuals did have 4-fold SBA rises by day 4. By day 10 there were large significant increases in the levels of SBA, IgG, IgM and IgA with respective fold increases from pre-vaccination levels of 4.6, 1.9, 1.2 and 2.1 in the MACP group and 270, 13.4, 4.8 and 33.8 in the naïve group. Further significant increases were seen between day 10 and 28 for SBA, IgG and IgM (naïve group only). By day 28, 4-fold SBA rises had occurred in 63.5% of the MACP group and 97.6% of the naïve group. The SBA GMT on day 28 significantly differed between the naïve and MACP groups with GMTs 2.8-fold higher in the naïve group (P = 0.021). In conclusion, no decline in serogroup C-specific antibody levels was demonstrated immediately post-MCC vaccination whilst these levels had risen significantly by day 10. Putative protective SBA titres (> or =8, 32 or 128) were observed by day 10 following MCC vaccination regardless of MACP history.