A new meningitis vaccine (MenAfriVac) is highly effective at protecting against epidemic A meningococcal disease, common in Africa’s meningitis belt where it accounts for at least three quarters of cases, and against transmission of the bacterium that causes these epidemics, according to new research published in The Lancet.
One shot of MenAfriVac dramatically reduced incidence of all cases of meningitis by 94% and carriage prevalence of the epidemic strain by 98%, while an epidemic persisted in unvaccinated parts of Chad.
“Until now, it was not known definitively whether MenAfriVac had a major impact on the incidence of serogroup A epidemics and carriage”, explains lead author Professor Brian Greenwood from the London School of Hygiene & Tropical Medicine.
“Before this study, mass vaccination campaigns in countries such as Burkina Faso had shown MenAfriVac to be safe and highly effective, resulting in the lowest number of confirmed meningitis A cases in over a decade. But in Burkina Faso the vaccine was introduced at a time of falling incidence rates and decreasing transmission, potentially enhancing its true effect and making it difficult to study the vaccine’s impact.”
This new study by the African Meningococcal Carriage Consortium was designed to compare the effect of MenAfriVac, a meningococcal A conjugate vaccine, on meningitis and meningococcal carriage in vaccinated and unvaccinated regions at the same time during an epidemic.
Deadly epidemics of meningitis A occur regularly in Africa’s meningitis belt, a band of 21 countries extending from Senegal to Ethiopia, where around 450 million people are at risk.
The researchers compared incidence rates between individuals aged 1-29 years vaccinated with one dose of MenAfriVac in December 2011 in three regions of Chad (roughly 1.8 million individuals vaccinated) and individuals in the remaining unvaccinated parts of the country.
During the 2012 epidemic season, the incidence of meningitis of any kind in the three vaccinated regions was 2.47 per 100 000 (57 cases in the 2.3 million total population), compared with 43.8 per 100 000 (3809 cases per 8.7 million population) in areas without mass vaccination.
What is more, despite enhanced surveillance, not a single group A meningitis case was identified in the three vaccinated regions, while 59 cases were confirmed in unvaccinated areas.