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Limited Vaccine Supply Threatens Response to Meningitis Epidemics
February 15, 2007
Barely two months into Africa's dry season, there are several countries facing severe outbreaks of meningitis. Doctors Without Borders/Médecins Sans Frontières (MSF) is already responding to epidemics in the Democratic Republic of Congo, southern Sudan, and northern Uganda. All three countries are in the southern tip of Africa's so-called "meningitis belt." This region, which is highly prone to epidemics, has 300 million inhabitants and stretches from Senegal in the west to Ethiopia in the east. Dr. Cathy Hewison, MSF's meningitis specialist, answers questions about the risks for a wide-scale epidemic this year and the current availability of vaccines.
What are the risks for a widespread epidemic of bacterial meningitis this year?
The World Health Organization carried out a risk assessment for this year and they looked at several indicators. Last year, a new serotype of the A strain of meningitis (Neisseria menigiditis A strain ST-2895) was identified during outbreaks in Niger and Burkina Faso. This could be one indicator that this season could be even worse in terms of epidemics. Another indicator is the emergence of epidemics in countries that have been quiet for a while, so last year there were smaller epidemics in Sudan and in Nigeria. What happens when several countries get into epidemics at the same time is that you can have a wave of epidemics. Between 1995 and 1997, there was a widespread epidemic across the "meningitis belt" that caused more than 25,000 deaths and 250,000 cases. And that is also what could happen in the next two seasons.
Is there an adequate supply of vaccines to deal with major epidemics?
There are just 25 million doses of A/C vaccine–the A strain being the most common cause of epidemics–available worldwide. Only 7 million doses have been reserved for epidemic responses. And the future prospects for replenishing the supply are bleak. In May, Sanofi-Pasteur, the sole provider of the A/C vaccine, announced that it was stopping production altogether while it transfers its production to another site. As a result, there will be no capacity to produce additional vaccines this year. It is extremely worrying when you consider that in Nigeria in 1996, more than 13 million people had to be vaccinated over the course of that epidemic.
How is the limited supply of vaccines managed?
The 7 million A/C vaccines were set aside by Sanofi-Pasteur and will only be sold to countries that have approved requests from an inter-agency body called the International Coordinating Group (ICG) on Vaccine Provision for Epidemic Meningitis Control, of which MSF is a member. The ICG was formed in order to protect the limited stock of available vaccines and prioritize their use for countries experiencing epidemics. The rest of the existing stock is available for countries to buy from the manufacturer. And some countries in high risk areas have already procured emergency stocks. There is also a limited stock (3 million doses) of trivalent vaccine for strains A, C, and W135 that is paid for and put aside by the ICG for use in cases of an epidemic caused by the W135 strain. Additional stocks of this vaccine need to be paid for before manufacture begins.
Because the overall supply of A/C vaccine is so limited, doses from the ICG supply are released only when an epidemic threshold–typically 10 or 15 cases per 100,000 people per week–has been crossed in a particular area. The vaccines are released to cover both areas that are already experiencing an epidemic and adjacent areas that are in the "alert" phase. The ICG reviews vaccination plans to ensure that the vaccines will be used in an efficient and rational way. The ICG also provides technical advice to countries or agencies responding to meningitis epidemics.
Are there any other options if the "meningitis belt" is hit with a massive epidemic?
Faced with a possible shortage of vaccines, MSF's epidemiological research arm, Epicentre, Folkehelseinstituttet, and Mbarara University of Science and Technology tested whether smaller doses of the vaccine would work. The results of this study, which was conducted in Uganda last year, showed that one-fifth of the normal vaccine dosage was 80 to 90 percent effective against the A strain. Now, this could have real implications for the response to a major epidemic. For example in a big country like Nigeria, if there is an enormous epidemic that requires 15 million vaccines and they aren't available, the government may have to decide whether to vaccinate 15 million people with 80 percent efficacy or 3 million people with 90 percent efficacy. So it is not a solution per say, but it is a possibility if the epidemics are enormous and there aren't any other options.
What are the prospects for a longer lasting vaccine?
The current polysaccharide vaccine only lasts up to three years, so countries in the "meningitis belt" are stuck in a cycle of epidemics. There is hope on the horizon, though, as researchers are testing a conjugate vaccine for the A strain that could provide longer protection. The conjugate vaccine has the potential to have a long lasting effect and could stop all epidemics in Africa. It could be used during epidemics, but the goal would be to vaccinate everybody across the "meningitis belt." The conjugate vaccine is currently in clinical trials. Unfortunately, the earliest this conjugate version would be widely available is 2012.
What is being done in the meantime to solve the supply problem?
MSF is working with the World Health Organization to find alternative sources of the current vaccine with companies in Brazil and Cuba. There are manufacturers in these countries that are WHO pre-qualified for vaccine production for yellow fever, for instance, but not meningitis. The earliest we can expect any dividends from this effort is for next season. We really need these short-term alternatives until the conjugate vaccine becomes available. Now you can see why no one is interested because there is a solution in five years time. So no one really wants to invest a lot of money in the immediate needs.
WHAT IS MENINGITIS
Cause:Bacterium Neisseria meningitidis. Strains A, B, C, Y, and W135 are the most common. Infected people typically carry the disease without showing symptoms and spread the bacteria through coughing and sneezing.
Symptoms:Meningitis causes sudden and intense headaches, fever, nausea, vomiting, photophobia, and stiffness of the neck. Death may occur within hours of the onset of symptoms.
Prevalence:Meningitis occurs sporadically throughout the world, but the vast majority of cases and deaths are in Africa. Epidemics regularly hit countries in the area referred to as the African "meningitis belt," which stretches across the continent from Senegal to Ethiopia. The total population at risk in these countries is around 300 million.
Treatment:Without treatment, bacterial meningitis kills up to 50 percent of infected people. Even if the disease is diagnosed early and treated with appropriate antibiotics, such as chloramphenicol or ceftriaxone, the case fatality rate remains 5 to 10 percent. As many as one out of five survivors will suffer from neurological after-effects such as deafness or mental retardation.
Vaccination:Timely mass vaccinations are the most effective means of limiting the spread of epidemics. The World Health Organization (WHO) has estimated that mass immunizations have managed to prevent up to 70 percent of expected cases in individual meningitis outbreaks in Africa.
SOURCE: World Health Organization