Meningococcal carriage in the African meningitis belt

Abstract

A meningococcal serogroup A polysaccharide/tetanus toxoid conjugate vaccine (PsA-TT) (MenAfriVac(™) ) is being deployed in countries of the African meningitis belt. Experience with other polysaccharide/protein conjugate vaccines has shown that an important part of their success has been their ability to prevent the acquisition of pharyngeal carriage and hence to stop transmission and induce herd immunity. If PsA-TT is to achieve the goal of preventing epidemics, it must be able to prevent the acquisition of pharyngeal carriage as well as invasive meningococcal disease and whether PsA-TT can prevent pharyngeal carriage needs to be determined. To address this issue, a consortium (the African Meningococcal Carriage (MenAfriCar) consortium) was established in 2009 to investigate the pattern of meningococcal carriage in countries of the African meningitis belt prior to and after the introduction of PsA-TT. This article describes how the consortium was established, its objectives and the standardised field and laboratory methods that were used to achieve these objectives. The experience of the MenAfriCar consortium will help in planning future studies on the epidemiology of meningococcal carriage in countries of the African meningitis belt and elsewhere.

Keywords: Africa; MenAfriCar; Neisseria meningitidis; meningococcal carriage; meningococcal vaccines; meningococcus.

Figure 1

Map of the meningitis belt showing the situation of the study centres sites based on the original description by Lapeyssonnie [1] (hatched areas) and additional areas (dotted) where the epidemiology of meningococcal disease has subsequently been shown to be characteristic of the meningitis belt.

Figure 2

Gantt chart showing the timing of different MenAfriCar carriage surveys.

Figure 3

Flow diagram indicating the procedure for isolating and characterising Nesisseria meningitidis isolates from oropharyngeal swabs.