Control of meningococcal infection in the African meningitis belt by selective vaccination.

During an outbreak of group-A meningococcal meningitis, information was collected on the distribution of cases of this infection in an area in northern Nigeria. More than 1 case was recorded in all but 3 of 23 affected villages. Members of 9 villages, with a population of about 10 000, in which there had been 2 cases of meningococcal disease were vaccinated with 50 microgram of group-A and group-C meningococcal polysaccharide vaccine. There were subsequently 10 cases of meningococcal disease in these villages but only 2 of these patients had been vaccinated. In contrast there were 38 cases of meningococcal disease in 7 control villages with a similar population. Until we have more information on the duration of immunity after meningococcal vaccination, selective vaccination may be a more cost-effective means of controlling meningococcal disease in the African meningitis belt than routine mass immunisation.