Meningococcal vaccines for the United Kingdom.

New meningococcal vaccines are needed in the United Kingdom with some urgency. Almost all Neisseria meningitidis disease in this country is caused by serogroups B and C. Infants have the highest attack rates, but also make the poorest immunological responses to potential vaccines. The development of vaccines that protect infants is a significant challenge. A capsule-based serogroup B vaccine is unlikely to be successful in infants because the capsule is poorly immunogenic and the polysaccharide molecule mimics a human epitope. Without completely discounting capsule as an immunogen, alternate antigens are being considered for immunisation: outer membrane proteins (OMP), iron regulating proteins, and lipopolysaccharide. Vaccines based on OMP have been used in several phase 3 trials in South Africa, Cuba, Brazil, Norway, and Chile, in which two doses of vaccine were given. The Cuban and Norwegian vaccines have been compared in phase 2 trials in Iceland and Chile. Potential limitations are epitope heterogeneity and the theoretical ability of N. meningitidis to adapt even to hosts who have received polyvalent vaccines. A phase 2 trial of a hexavalent class 1 OMP vaccine is under way in Gloucester, with 100 babies receiving injections at 2, 3, and 4 months. Serogroup C vaccines have been developed from capsular polysaccharide but, unconjugated, these vaccines do not protect those under 2 years of age. Conjugate vaccines with C and AC polysaccharides are immunogenic in infants, but antibody titres may wane quickly.(ABSTRACT TRUNCATED AT 250 WORDS)