Meningitis epidemics caused by the pathogen Nesseiria meningitis (or meningococcus) provoke high mortality in children and young people under 20 years of age in sub-Saharan Africa. They rage during periods of drought from January to April, in the area known as the Meningitis Belt (see Map)
Two types of vaccine are currently on the market: the polysaccharide vaccine and the conjugated vaccine. The polysaccharide form, elaborated from a sugar present at the surface of the meningococcus provides only partial, temporary immunity in very young children (2).
The conjugated vaccine, however, is based on a combination between this same sugar and an antigenic protein and renders an effective durable immunity. It could therefore be used in a routine preventive vaccination campaign. But it is costly. Its high price, at 11 to 22 euros per dose, means it remains inaccessible for African countries. These have available only the polysaccharide vaccine, less expensive at 0.3 to 0.5 euro, but which, because of its low immunity capacity, is generally kept only for emergency vaccinations, when epidemics occur.
IRD researchers have been running a follow-up study of the people of the Niakhar region (located 150 km from Dakar, in Senegal) for more than 40 years. They looked into the question of the ability of the polysaccharide vaccine to prevent the occurrence of meningitis cases during epidemics in the course of subsequent years. To do that, they made use of results of two vaccination campaigns conducted with this vaccine by the Senegalese health services. One of these was run in 1996 in 8 of the 30 villages that make up the Niakhar region, the other in 1999, in the whole of the study area, hit be a series of epidemics between 1998 and 2000.
Using quarterly censuses carried out since 1983, the researchers collected then analysed data on childrens state of health and vaccine status. They could therefore make comparisons between the different villages regard
Contact: Marie Guillaume
Institut de Recherche Pour le Dveloppement