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Meningococcus

Meningococcus (Neisseria meningitidis) has 13 known serotypes with groups A, B, and C being the most common causes of disease worldwide. Meningococcal A epidemics kill several thousand people each year in the African meningitis belt, mainly affecting infants and young children. Meningococcal disease can be treated with antibiotics; however, even with adequate antibiotic treatment, at least 10 percent of patients die within 48 hours of onset of symptoms, while a further 10 to 20 percent of survivors develop severe disabilities. Existing multivalent vaccines are expensive and, while effective against the serotypes included, do not cover all the disease causing strains in the developing world.

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Meningococcal disease

  • Meningococcus (Neisseria meningitidis) has 13 known groups. Groups A, B, C, Y, and W account for almost all cases of disease. Groups A, B, and C are the most common causes of disease worldwide.
  • The meningitis belt of sub-Saharan Africa, stretching from Senegal in the west to Ethiopia in the east, has the highest disease rates.
  • Group A meningococcus accounts for an estimated 80 to 85 percent of all meningitis epidemics in the region, with epidemics occurring at intervals of 8 to 10 years.
  • Meningococcal A epidemics kill several thousand people each year in the African meningitis belt (26 countries and a population of about 450 million).
  • Meningococcal X is an emerging serotype that has caused epidemic meningitis in recent years in Africa and for which there is currently no licensed vaccine.
  • Meningococcal disease mainly affects infants and young children, but also can readily be found in older children and young adults.
  • Up to 10 to 25 percent of a population may be asymptomatic carriers in non-epidemic settings. However, the carriage rates may be higher in epidemic situations.
  • Most cases of meningococcal disease are acquired by person-to-person contact through droplets or contact with respiratory secretions from asymptomatic carriers.
  • The most common presentation of meningococcal disease is acute meningitis characterized by fever and chills, intense headache, stiff neck, vomiting, lethargy or drowsiness, or irritability. Less commonly, patients present with meningococcal septicemia, a catastrophic constellation of fever, purpuric rash, multiorgan failure, and shock of frighteningly rapid onset.
  • Meningococcal disease is treated with antibiotics. However, even with adequate antibiotic treatment, at least 10 percent of patients die within 48 hours of onset of symptoms, while 10 to 20 percent of survivors develop severe sequelae, including brain damage, hearing loss, or learning disabilities. Left untreated, the disease can lead to fatality rates greater than 50 percent. Vaccination is critical.

Meningococcal vaccine

  • Multivalent polysaccharide vaccines (against groups A and C; A, C, and W; or A, C, Y, and W) are licensed (Bio-Manguinhos, GlaxoSmithKline, and Sanofi-Pasteur) and available worldwide. Polysaccharide vaccines have been available for over 30 years, but they are poorly immunogenic in infants and children less than two years old, fail to induce immunological memory, do not induce herd immunity, and do not provide protection for more than two to three years.
  • Development of a vaccine against group B meningococcal disease has been problematic. One vaccine was recently licensed in Europe and Australia (Bexsero®, Novartis). Several other vaccine candidates are in clinical testing.
  • Since 1999, meningococcal conjugate vaccines against group C have been available and widely used in Europe and Canada (Baxter, Chiron, and Wyeth). Tetravalent A, C, Y, and W conjugate vaccines have also been licensed for use in children and adults in the United States, Canada, and Europe (Sanofi-Pasteur, Novartis, and GlaxoSmithKline).
  • In December 2010, a new meningococcal conjugate vaccine against group A, MenAfriVac™, was introduced in Africa. Developed by the Meningitis Vaccine Project, a PATH-World Health Organization partnership, the vaccine was given to more than 100 million individuals aged 1 to 29 years as of 2013, with an additional 230 million people expected to be vaccinated by 2016. The vaccine has several advantages over existing polysaccharide vaccines: it induces a higher and more sustainable immune response against group A meningococcus; it is expected to confer long-term protection not only for those who receive the vaccine, but on family members and others who would otherwise have been exposed to meningitis; it is available at a lower price than other meningococcal vaccines; and it is expected to be particularly effective in protecting children under two years of age, who do not respond to conventional polysaccharide vaccines.

Related diseases

There are several key causes of childhood pneumonia and meningitis (inflammation of the covering of the brain), including pneumococcus, Haemophilus influenzae type b (Hib), and meningococcus bacteria. Learn more about pneumococcus. Learn more about Hib.

References

Page last updated: November 2013.

Photo: PATH/Gabe Bienczycki.