Meningococcal meningitis is a bacterial infection of the meninges (three membranes that envelop the brain and spinal cord) specifically caused by Neisseria meningitidis bacteria with 12 serogroups, six of which can cause outbreaks (A, B, C, W, X and Y). A group of 26 sub-Saharan African countries form part of the high transmission area known as the “meningitis belt” (from Senegal in the west to Ethiopia in the east). Historically in this area, before the introduction of mass preventive immunisation campaigns, 80% of cases were caused by serogroup A meningococcus (Men A) during seasonal outbreaks occurring at intervals of 7 to 14 years during the dry season.
The infection is transmitted by person-to person through air droplets of respiratory secretions. Close and prolonged contact (kissing, living in close quarters) enhances transmission. Most people who become infected carry the bacteria harmlessly in their throat. However, in some people disease may develop shortly after infection. Symptoms of meningococcal disease include headache, stiff neck, and high fever, sensitivity to light, confusion, headaches and vomiting. The disease progresses to a severe stage in a brief period; the fatality rate is 10-15%, and higher without antibiotic treatment (antibiotics against N.meningitidis). Among survivors, 10-20% are left with severe permanent disabilities such as paralysis, blindness and hearing loss.
Several vaccines to prevent meningococcal disease are available. For instance, MenAfriVac®, a conjugated vaccine against serogroup A and specially designed for use in the poorest regions due to its thermostability and low costs, has been used for mass preventive immunisation campaigns. This vaccine has several other advantages compared to previous vaccines such as: higher and more sustainable immune response against group A meningococcus, significant reduction of carriers of the bacteria, long-term protection, and high effectiveness in protecting children under 2 years of age, who do not respond to conventional polysaccharide vaccines.
The MenAfriVac vaccination strategy is mainly planned around campaigns to immunise the at-risk population (aged from 1 to 29 years). Gavi, the Vaccine Alliance, has supported the “meningitis belt countries” with preventative vaccination campaigns, routine immunisation, catch-up vaccination campaigns to immunise the children born between the start of campaign vaccinations and the start of routine immunisations, and maintenance of a vaccine stockpile for emergency response. Since the strategy has been implemented, incidence of serogroup A has decreased by >99%. As of December 2016, over 260 million people (aged from 1 to 29 years’ age) within 19 countries have received the meningococcal A conjugate vaccine. There is growing concern however about outbreaks due to other serogroups, such as C and W, that have been reported in recent years.