Recent developments in Neisseria meningitidis group A conjugate vaccines.

Meningococcal disease, both endemic and epidemic, remains a major cause of meningitis in many countries. Protective immunity is mediated primarily by bacteriocidal antibodies against the capsular polysaccharides for serogroups other than B, and against non-capsular surface components for group B. This article focuses on the development of conjugate vaccines for serogroup A, with special emphasis on the needs of Africa. The first licensed (1999) meningococcal conjugate was against group C in the UK and was > 90% effective in infants, children and young adults. The problem now is to develop a highly immunogenic group A meningococcal conjugate vaccine for use in developing countries as an alternative to the presently licensed group AC polysaccharide vaccine. Immunogenicity studies on the group A polysaccharide show the polysaccharide itself to be uniquely immunogenic in young children compared with other polysaccharides, making comparative studies with a highly immunogenic conjugate of considerable importance.