Meningococcal serogroup C-specific IgG antibody responses and serum bactericidal titres in children following vaccination with a meningococcal A/C polysaccharide vaccine

In the UK, a co-ordinated series of phase II studies is being undertaken wi th meningococcal serogroup C conjugate (MCC) vaccines. The use of meningoco ccal A/C polysaccharide (MACP) vaccines in control arms in young children h as been avoided because of the well recognised short comings of these vacci nes. Following a cluster of serogroup C disease centred on a day nursery, i ntervention by MACP vaccination was performed as an outbreak control measur e. Using this cohort, serogroup C-specific IgG ELISA and serum bactericidal assays (SBA) were performed using both de-O-acetylated (Oac(-)) and acetyl ated (Oac(+)) serogroup C antigen, the measurement of primarily high avidit y antibody and using baby rabbit or human complement in the SEA. The effect of subject age (either less than or greater than 2 years of age) was asses sed for the different assays and significant differences (P < 0.05) were fo und using both antigen sources in the high avidity ELISA and in the rabbit complement SEA but not in the standard ELISA. When assessing results from d ifferent studies it is important that methodologies utilised allow such com parisons since the choice of reagents can have a profound influence. The im portance of standardised assays is paramount at a time where immunogenicity trials are replacing efficacy trials for the introduction of MCC vaccines. (C) 2000 Federation of European Microbiological Societies. Published by El sevier Science B.V. All rights reserved.