Neisseria meningitidis is found naturally in the back of the throat or nose and will only occasionally cause disease. It is unknown why some individuals carry the bacteria without harm while others go on to develop meningococcal disease. Approximately 10% of the population will carry Neisseria meningitidis, with the highest carriage (~25%) in 15-19 year olds. Infection is not easily spread. It is transmitted from person to person by inhaling respiratory secretions from the mouth and throat or by direct contact (kissing). Close prolonged contact is usually required to transmit the bacteria. They do not live long outside the body.

The majority of meningococcal infections occur in infants less than five years of age, with a peak incidence in those under 1 year of age. There is a smaller, secondary peak in incidence in young adults aged between 15 – 19 years of age. 

Most cases of meningococcal disease occur sporadically, with less than 5% of cases occurring in clusters. Outbreaks of meningococcal disease are more common among teenagers and young adults, and outbreaks have been reported in schools and universities. Public health interventions may include vaccination (depending on serogroup) and chemoprophylaxis.

Meningococcal disease shows marked seasonal variation with a peak in winter and a low level in summer. The winter season coincides with that of influenza.

Meningococci are divided into distinct serogroups, according to their polysaccharide outer capsule. The most common serogroups that cause disease worldwide are groups B, C, A, Y and W135. Most disease in the UK is caused by serogroups B and C. 1996 - 2000 figures, showed serogroup B accounted for 59% of all cases, group C (36%) and other groups including W135 & A (5%)

Benzylpenicillin:

Meningococcal disease has a case fatality rate of approximately 10%, however, more deaths are caused by septicaemia than by meningitis, but the best outcomes are seen with early antibiotics.

The UK was the first country in the world to introduce meningococcal serogroup C conjugate (MenC) vaccination.  Immunisation with  (MenC) vaccine started in November 1999 for everybody up to the age of  18 years, and to all first year university students. This has since been extended to include everybody under 25 years of age.

Three MenC vaccines are licensed in the UK and these are considered to be interchangeable. The MenC vaccine does not protect against other meningococcal disease caused by other serogroups (A, B, W135, Y).

As the vaccine does not protect against serogroup B meningococcal disease ( currently responsible for the majority of meningococcal infections), it is of the utmost importance that health professionals and the general public remain alert to the signs and symptoms of meningococcal disease.  Work is currently being undertaken to develop a group B meningococcal vaccine. However, the variability of the group B meningococcus means that a  group B vaccine for meningococcal disease will not be available for sometime.