Despite a relatively calm meningitis epidemic season (January-June 2018), the risk of large-scale epidemics remains high. A convergence of factors is threatening the region with large outbreaks affecting millions since 2015. A new hyper-invasive strain of meningococcal meningitis serogroup C is circulating at the same time that an acute shortage of meningitis C-containing vaccine threatens to severely limit the region’s ability to minimize the number of persons affected.
The new serogroup C strain now represents the major risk of meningitis outbreaks in the region. While this season cases due to Nm C decreased, still 5000 suspected cases were reported in Niger and Nigeria alone. In 2017 the Nm C strain had caused 18,000 cases in Nigeria and Niger. This pattern was also observed in 2016, where a calm season (or reduction in cases) was observed after a devastating Nm C epidemic in Niger and Nigeria in 2015, which had caused 12,000 cases. This calm season was followed by a huge epidemic in 2017. Nm C attack rates can be very high (up to 990 cases/100,000, as observed in Niamey in 2015), population immunity is low, the strain is already circulating in neighboring countries of the African meningitis belt (Burkina Faso, Mali, Cameroun) and it showed a potential to spread outside the belt as observed in Liberia.
Urgent action is needed to prepare for the worst and minimize the potentially devastating impact of outbreaks in the region. But stocks of C-containing vaccine are alarmingly inadequate. WHO continues to call on technical and operational partners, vaccine manufacturers, and donors to act now to increase the availability of meningococcal vaccines that protect against serogroup C. The ICG emergency international stockpile has just 3.4 million doses of C containing vaccine for 2019. The immediate need is for an additional 1.6 million doses, in priority conjugate vaccines. Despite the high cost, they offer the best prospects for disease control by offering a long-lasting immune response.
Meningitis epidemics in the African meningitis belt constitute an enormous public health burden. Shortages of vaccine to control the new hyper-invasive strain portend a catastrophe with potential to affect as many as 34 million persons in the region. By raising the alert now, WHO hopes to close the critical vaccine gap and keep this highly feared disease from sweeping across and potentially beyond West Africa.