Prevention of group B meningococcal disease by vaccination: a difficult task.

New Zealand has embarked on an immunisation program to reduce the incidence of disease caused by serogroup B Neisseria meningitidis. Similar immunisation programs in Norway and South America have shown good efficacy in older vaccinees (ie, persons receiving vaccinations), but variable efficacy in younger vaccinees. Protective efficacy correlates well with the ability of the vaccine to stimulate a fourfold rise in serum bactericidal antibodies. Unfortunately, second and third doses of serogroup B N. meningitidis vaccines do not boost serum bactericidal antibody titres to very high levels; consequently protective efficacy wanes within a few years of immunisation. The overall outcome of the immunisation program will reflect both the immunogenicity of the vaccine and the uptake of the vaccine by the target population. The especially high incidence of meningococcal disease in Pacific and Maori children means that particular efforts will need to be made to reach these groups.