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Chemoprophylaxis of meningitis.

'If it is preventable, why not prevent it?' is a legitimate starting point in the discussion of infections, particularly communicable infections. How does this aphorism stand in regard to meningococcal and Haemophilus influenzae meningitis? Although vaccines are available and licensed in the United States for protection against infection with meningococci (Sero groups A, C, Y, and W135 but not B)' and H influenzae type B,2 they are not generally available in the United Kingdom, and prevention of these forms of meningitis relies on chemoprophylaxis. Meningococcal meningitis has long been recognised as infectious-that is, communicable from one individual to another; worldwide epidemics are part of the published reports. The organism resides in the nasopharynx of a proportion of the population who are for the most part asymptomatic, and droplet spread is responsible for communication to other subjects, a tiny proportion of whom, susceptible in an ill understood way, develop invasive disease. Crowded living conditions, as in barracks, leads to increasing acquisition rates of meningococci and a rising incidence of meningitis. The prevention of colonisation and, by implication, invasion by meningococci, would therefore seem a rational aim, and this is the theoretical basis for the present policy of administering antibacterial agents to close contacts of known cases. Plausible though the policy appears, is it practical and does it work? It is certainly practical in the sense that drugs (rifampicin, sulphonamides, and minocycline), when administered to controls, do reduce carriage and the incidence of disease. We know that 70% of secondary cases of meningococcal meningitis occur within one week of the confirmation of the index case; it could therefore be argued that what is really happening in the context of chemoprophylaxis is that very early cases are being treated, but it should be pointed out that penicillin, which is so effective in treatment of cases, does not prevent carriage or indeed the development of invasive disease when it is used prophylactically. It may be that the pharmacodynamics of individual drugs is responsible for their usefulness or otherwise in prophylaxis. Rifampicin, sulphonamide, and minocycline reach fairly high concentrations in the saliva, whereas penicillin does not. Rifampicin or sulphonamide (where sensitive strains are present) are now recommended as chemoprophylaxis in children and adults in the following doses: rifampicin: adults 600 mg twice