West African meningitis outbreak strains vaccine supplies

Abstract

This year's meningitis outbreak in west Africa, which UNICEF has called the worst in more than 5 years, has severely depleted limited global vaccine supplies. Wairagala Wakabi reports. With the meningitis outbreak this year having killed more than 2500 people in Africa's so-called meningitis belt, shortage of vaccines has been blamed for the high case fatality rate (CFR) seen in some countries. The International Coordination Group (ICG)—the WHO-led interagency group that coordinates meningitis vaccines—said by the end of April it had approved 9·1 million doses of vaccine from “the limited global stockpile” for the outbreak. This was much higher than the 2 million doses approved for the entire 2007–08 season. Aphaluck Bhatiasevi, media officer at the Epidemic and Pandemic Alert and Response department at WHO, says that there have been sufficient vaccines to cover emergencies this year, but it took some countries a long time to access supplies at the ICG. This had in turn resulted in delays in the implementation of mass vaccination campaigns. The ICG has this year had a large emergency stockpile (12 million doses), but the remaining supply for the market, which stood at 13 million doses, was very limited. “This situation hampered the capacity of the countries to build their national stockpiles, making them more dependent on the emergency stockpile”, said Bhatiasevi. To access the emergency stockpile, countries have to submit a request to the ICG with precise information and this process in some cases resulted in delays in implementing mass vaccination. According to UNICEF, the countries most affected by the epidemic were Nigeria, Niger, Burkina Faso, and Chad. Early in May, the Nigerian Health Ministry reported that the meningitis outbreak in the country had been more serious than initially thought. The ministry said 2148 people had died since December, 2008, and the number of reported cases stood at 47 902. Marie Yherese Guigui Zoundi, health specialist at UNICEF for West and Central Africa, said in Burkina Faso the CFR has been higher than usual because the bacterium causing meningitis is the pneumococcus, which seems to be more virulent than the meningococcus bacterium involved in other countries. However, in other countries the CFR has been lower than in previous years even though more people have been affected. In the two previous years, average CFR for the countries of the belt were 8% and 10%, compared with 5% this year. “We are currently investigating and trying to understand the reasons of the rather low CFRs reported this year”, said Bhatiasevi. An estimated 450 million people in 21 African countries are at risk of meningitis, with children, adolescents, and young adults especially threatened. WHO says the largest recorded meningitis outbreak in Africa occurred in 1996–97 when an estimated 100 000 people were infected in Nigeria and 50 000 in Niger. According to WHO officials, by early May a drop in cases was being registered across the belt, particularly in the most affected countries. “The data clearly indicates that the epidemic season is getting to an end”, said Bhatiasevi. “However, there are a few hot spots remaining in those countries that still require intervention. Mass vaccination is still ongoing in those areas and measures to ensure free access to treatment are being maintained.” In the meantime, UNICEF and WHO are supporting affected countries to mobilise vaccines and strengthen their epidemic response. More crucially, better vaccines should be available later this year to boost the fight against meningitis in Africa. “The current strategy which is reactive rather than preventive is heavily conditioned by the characteristics of the meningitis polysaccharide vaccines available. Nevertheless, a new meningococcal conjugate vaccine against serogroup A, the main cause of meningitis epidemics in the belt, is expected to be available in Africa by the end of 2009”, said Bhatiasevi. The development of this new vaccine was the result of a partnership between WHO and the international non-governmental organisation PATH. “The immunogenic characteristics and the price of this vaccine (US$0·40) makes possible the shift to a preventive strategy and makes the elimination of meningitis A epidemics as a public health problem feasible in the long term”, said Bhatiasevi.