Successful African introduction of a new Group A meningococcal conjugate vaccine: Future challenges and next steps

Abstract

The introduction of a new Group A meningococcal conjugate vaccine, MenAfriVac^R, has been a important public health success. Group A meningococcal meningitis has disappeared in all countries where the new Men A conjugate vaccine has been used at public health scale. However, continued control of Group A disease in sub-Saharan Africa will require that community immunity against Group A meningococci be maintained. Modeling studies have shown that unless herd immunity is maintained Group A meningococcal disease will return. To ensure that African populations remain protected birth cohorts must be protected with an EPI formulation of MenAfriVac^R (5 mcg) given at 9 months with Measles 1. In addition, populations born after the initial 1-29 year old campaigns and consequently not yet immunized with the new Men A conjugate vaccine, will have to be immunized in country-specific catch-up campaigns. Countries with poor EPI coverage (Measles 1 coverage < 60%) will likely need quinquennial vaccination campaigns aimed at covering 1-4 year olds. Implementing these strategies is the only sure way of ensuring that Group A meningococcal meningitis epidemics will not recur. A second problem that requires urgent attention is the challenge of dealing with Non-A meningococcal meningitis epidemics in sub-Saharan Africa. Groups C, W and X meningococci are well-established circulating strains in sub-Saharan Africa and are responsible for yearly focal meningitis epidemics that vary in severity and remain unpredictable as to size and geographic distribution. For this reason, polyvalent meningococcal conjugate vaccines that are affordable and appropriate for the African context must be developed and introduced. These new meningococcal vaccines when combined with more affordable pneumococcal conjugate vaccines offer the promise of a meningitis-free Sub-Saharan Africa.

Keywords: Epidemic meningitis; conjugate vaccines; herd protection; neisseria meningitidis.