Meningococcus, also called Neisseria meningitidis, is a bacterium that is capable of causing severe infections in human beings. It is the principal cause of bacterial meningitis, a life-threatening illness, in adults. It can also cause dangerous bloodstream infection without signs of meningitis. The attack rate is approximately 1 case per 100,000 population per year. This works out to about 2500-3000 cases annually in the United States.
Most cases occur in children, among whom fatality rates are also higher.
Recent highly publicized epidemiologic studies, carried out in limited geographic areas, have suggested that the incidence of meningococcal disease may be higher in college students who live on campus than in those who live at home. The germ is spread from person to person by direct contact and in saliva and respiratory secretions. This is a vaccine prepared from killed meningococci which, when injected into the body, stimulates the immune system to produce antibody against the germ. Five serotypes of meningococci have been identified as causing human disease. The currently available vaccine protects against four of these.