Seroprevalence of meningococcal serogroup C bactericidal antibody in England and Wales in the pre-vaccination era

Sera from an age-stratified sample of 1689 individuals, submitted to the PHLS Seroepidemiology Unit between 1996 and 1999 were tested for serum bactericidal antibodies to serogroup C meningococci. Titres decreased during infancy, presumably as maternal antibody waned, and increased in older teenagers, the peak age of meningococcal carriage. The prevalence of antibody titres greater than or equal to 8 was highest in adults, with an average of 25% of adults 25 years old or above with titres above this putative protective level. In the absence of vaccination, antibody may be generated from periods of carriage of serogroup C meningococci, from other meningococcal strains sharing non-capsular antigens, and other cross-reactive organisms. The inverse relationship between disease incidence and the prevalence of 'protective' antibody titres as described by Goldschneider et al. appears more consistent with a titre of greater than or equal to8 rather than greater than or equal to128, although the proportions 'protected' are much lower here than in Goldschneider's study. This study provides baseline antibody levels which will facilitate the evaluation of the meningococcal serogroup C conjugate vaccination programme. (C) 2002 Elsevier Science Ltd. All rights reserved.