Meningococcal vaccines are used for active immunisation against Neisseria meningitidis infections, which include meningitis and septicaemia. They are preparations of purified polysaccharide antigens from N. meningitidis and may be monovalent, containing the antigen of only one serotype of N. meningitidis or polyvalent, containing antigens of two or more serotypes. Conjugation of the polysaccharide to a carrier such as diphtheria CRM197 protein or to tetanus toxoid protein increases the immunogenicity.
In the UK, primary immunisation is recommended during infancy whereas in the USA routine immunisation is recommended during adolescence. In the UK, a conjugate meningococcal C vaccine is used and is generally given by intramuscular injection with the subcutaneous route reserved for patients with haemophilia or thrombocytopenia. Infants, starting at 2 months of age, are given 3 doses of 0.5 mL at monthly intervals. If primary immunisation is delayed until 5 months of age then 2 doses, one month apart, are sufficient; children over 1 year of age and adults should be given a single dose only. In the USA, routine immunisation with a single dose, given intramuscularly, of a conjugate tetravalent vaccine from groups A, C, Y, and W135 is performed at 11 to 12 years of age. For discussion of immunisation schedules see under Vaccines, .
Asplenic persons or those who have terminal complement component deficiencies are at higher than normal risk of acquiring meningococcal infection and therefore they should be immunised. Either a conjugate meningococcal C vaccine or a tetravalent vaccine (A, C, Y, and W135, unconjugated or conjugated) may be used depending on availability.
Meningococcal vaccines are also indicated in persons travelling to countries where the risk of infection is high. They should receive a tetravalent meningococcal polysaccharide vaccine (either unconjugated or conjugated) rather than the group C conjugate vaccine, and should be immunised even if they have already received the latter. Vaccination is indicated particularly for visits of 1 month or more and for those backpacking or living or working with local residents. Vaccination is a visa requirement for Hajj pilgrims to Saudi Arabia.
Meningococcal vaccines may be given as an adjunct to chemoprophylaxis in contacts of persons with meningitis (see ).
A meningococcal group B vaccine has been developed in New Zealand and contains outer membrane vesicles from N. meningitidis group B strain NZ 98/254. It is given for primary immunisation against the New Zealand strain (P1.7-b,4* PorA protein) of group B meningococcal disease. Adults and children over 6 months old are given three doses of 0.5 mL at intervals of 6 weeks intramuscularly; infants less than 6 months old should be given 4 doses, at 6 weeks, 3 months, 5 months, and 10 months of age. Vaccines against other group B meningococci are under investigation (see ).
- 1. Ruggeberg J, Heath PT. Safety and efficacy of meningococcal group C conjugate vaccines. Expert Opin Drug Saf 2003; 2: 7–19. PubMed
Despite the established use of vaccines against meningococcal groups A, C, W135, and Y, about 60 to 80% of meningococcal infections () in the UK and the USA are caused by Neisseria meningitidis of group B serotype. Unfortunately the purified group B polysaccharide is only poorly immunogenic, even after conjugation with proteins but several avenues of research are being followed in the development of an effective vaccine. These include vaccines based on other outer membrane proteins contained in outer membrane vesicles, in particular the most important outer membrane proteins, PorA, and on lipopolysaccharide derivatives. More recently, group B meningococcal vaccine based on PorA has been developed in New Zealand (see ) and is available for primary immunisation against the New Zealand strain specifically. Recombinant technology has been used in the Netherlands to develop both a monovalent PorA vaccine and a hexavalent vaccine containing 6 PorA proteins, including that of the New Zealand strain. Results obtained with the New Zealand PorA antigen in the hexavalent formulation have been poor, but it has been shown to stimulate a satisfactory immune response in infants or small children in the monovalent form. The successful sequencing of the meningococcal genome has allowed discovery of several new proteins and raised potential for the development of new candidate vaccines, including novel surface-located vaccine candidates which are currently in preclinical evaluation.
An intranasal meningococcal group B vaccine is also under development.