title: Emergence of serogroup X meningococcal disease in Africa: need for a vaccine.
abstract: Neisseria meningitidis is responsible for the seasonal burden and recurrent epidemics of meningitis in an area of sub-Saharan Africa known as the meningitis belt. Historically, the majority of the cases in the meningitis belt are caused by serogroup A meningococci. Serogroup C meningococci were responsible for outbreaks in the meningitis belt in the 1980s, while serogroup W (formerly W-135) has emerged as a cause of epidemic meningitis since 2000. Serogroup X meningococci have previously been considered a rare cause of sporadic meningitis, but during 2006-2010, outbreaks of serogroup X meningitis occurred in Niger, Uganda, Kenya,Togo and Burkina Faso, the latter with at least 1300 cases of serogroup X meningitis among the 6732 reported annual cases. While serogroup X has not yet caused an epidemic wave of the scale of serogroup A in 1996-1997 or serogroup W in Burkina Faso during 2002, the existing reports suggest a similar seasonal hyperendemicity and capacity for localised epidemics. Serogroup X incidence appears to follow a pattern of highly localised clonal waves, and in affected districts, other meningococcal serogroups are usually absent from disease. Currently, no licensed vaccine is available against serogroup X meningococci. Following the introduction of a monovalent serogroup A conjugate vaccine (MenAfriVac(®)) in the meningitis belt and the upcoming introduction of pneumococcal conjugate vaccines, vaccine-based prevention of serogroup X may become a public health need. The serogroup X polysaccharide capsule is the most likely target for vaccine development, but recent data also indicate a potential role for protein-based vaccines. A multivalent vaccine, preferably formulated as a conjugate vaccine and covering at least serogroups A, W, and X is needed, and the efforts for vaccine development should be intensified.
authors.affiliation: Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, OX3 7TU, UK.
authors.forename: Ouli
authors.initials: O
authors.lastname: Xie
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pollard
authors.forename: Judith E
authors.initials: JE
authors.lastname: Mueller
authors.forename: Gunnstein
authors.initials: G
authors.lastname: Norheim
mesh_terms: D017954:Africa South of the Sahara / Q000453:epidemiology; D035843:Biomedical Research; D004196:Disease Outbreaks; D006801:Humans; D015994:Incidence; D008585:Meningitis, Meningococcal / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D022401:Meningococcal Vaccines / Q000276:immunology*; D009345:Neisseria meningitidis / Q000276:immunology* / Q000302:isolation & purification; D018074:Vaccines, Conjugate / Q000276:immunology
chemical_list: C573970:MenAfriVac; D022401:Meningococcal Vaccines; D018074:Vaccines, Conjugate