Analysis of meningococcal serogroup C-specific antibody levels in British Columbian children and adolescents.

The effects of age, sex, and possible prior exposure to serogroup C meningococci on group C-specific antibody levels (total and functional) were examined in 2- to 19-year-olds just before and 1 and 12 months after immunization with divalent (groups A + C) meningococcal capsular polysaccharide vaccine. Only age was found to have a significant effect on antibody levels. At 1 month, only 50% of 2- to 6-year-olds had detectable serum bactericidal antibody, in contrast to 84.1% and 96.3% of 9- to 12- and 13- to 19-year-olds respectively. By 12 months, only 20%, 40.9%, and 53.8% of subjects in these age groups had serum bactericidal antibody, suggesting that current meningococcal C polysaccharide vaccines provide only short-term protection. However, the drop in total specific antibody levels (by EIA) was less pronounced. Persistence of antibodies detectable by EIA (but not serum bactericidal antibodies) suggests that this vaccine may also give rise to antibodies of low affinity or directed to nonfunctional (nonprotective) epitopes (or both).