Putting an end to meningitis season

  • August 28, 2012
Putting an end to meningitis season

In the region of Africa stretching west to Senegal and east to Ethiopia, the scorching dry season is known by another name: meningitis season. For more than a century, large-scale outbreaks of meningitis primarily caused by the bacteria Neisseria meningitidis have led to significant suffering.  As a result, meningococcal disease is a particularly feared disease in the countries of the meningitis belt. Patients experience a sudden onset of symptoms such as headache, fever, and a stiff neck and can die within 48 hours or sustain permanent cognitive and hearing impairment. Hundreds of thousands of cases and thousands of deaths occurred during the largest epidemic recorded, in 1996.

Meningococcal vaccines were first developed in the 1970s and have been used extensively to control epidemics in Africa. Unfortunately, these polysaccharide vaccines have a limited impact on preventing future outbreaks since they do not protect very young children and provide protection to older children and adults for only a few years.

When I first began collaborating with the Centre pour le Développement des VaccinsMali (CVD-Mali) in Bamako and the African Meningococcal Carriage Consortium (MenAfriCar) as a graduate student in 2009, a new opportunity to prevent meningitis outbreaks was on the horizon.

The Meningitis Vaccine Project (MVP) was formed through a partnership between the World Health Organization and the nonprofit health organisation PATH with funding from the Bill and Melinda Gates Foundation. MVP’s goal was to develop an affordable vaccine designed specifically for use in the meningitis belt, where Neisseria meningitidis serogroup A was the most common cause of meningitis at that time, using new conjugate technology to join the polysaccharides in the older vaccines to a protein, eliciting a stronger immune response.

Evidence from the UK, US, and other resource-rich nations where conjugate meningococcal vaccines were already in use indicated that these types of vaccines could protect very young children, induce a long-lasting immune response, and result in widespread protection in the population. Even though the technology already existed to produce this vaccine and similar vaccines were being used elsewhere with great success, the vaccines had not yet reached the resource-poor countries of the meningitis belt, the region of the world that needed them most. Not surprisingly, one of the largest barriers was cost. Conjugate meningococcal vaccines are available in the US for approximately $100-150 a dose.

The challenge for MVP was to create a new model for vaccine development that would overcome this barrier in countries like Mali where the per capita income in 2010 was less than $700 a year. After significant effort to secure a producer, conduct clinical trials, and acquire the necessary approvals, MVP marked an historic moment in December 2010 when the newly developed vaccine MenAfriVacTM was introduced in Burkina Faso, Mali, and Niger in the first-ever preventative campaign against meningococcal disease in Africa. Through a coordinated effort between partners across several countries and continents, nearly 20 million individuals aged 1 to 29 years were vaccinated during a four-week period. And the price of the vaccine? Forty cents a dose.

That no cases of meningococcal disease caused by serogroup A bacteria have been identified among the millions of vaccine recipients since then is an incredible step forward for public health. This is an encouraging sign, but only time will tell if this vaccine will completely eliminate serogroup A meningococcal disease from the meningitis belt. MVP continues to work to roll out the vaccine in other high-risk countries.

Photo: Nicole Basta (standing second from left) with CVD-Mali director Dr. Samba Sow (standing far left), members of the CVD-Mali field research team, and representatives from the MenAfriCar Consortium. Bamako, Mali, May 2010.

As an infectious disease epidemiologist, I am interested in understanding the transmission dynamics of infectious diseases, assessing the direct and indirect effects of vaccines and vaccination programmes, and determining optimal strategies for disease prevention and control. This December, I will launch a field study to address the number one question following the introduction of the MenAfriVac vaccine: how long will protection last? Through the “MenAfriVac Antibody Persistence” (MAP) study, we will enrol thousands of residents of Bamako, Mali, over the next five years to investigate the magnitude and duration of the immune response to this vaccine, identify risk factors that may lead to poor vaccine response, and determine whether protective immunity is maintained in the entire population over time or if booster doses or catch-up campaigns are needed. This research is supported by the US National Institutes of Health Director’s Early Independence Award and will allow me to continue to collaborate with colleagues at the CVD-Mali to address a significant and timely public health problem.

The history of the field of public health is full of stories of significant triumphs over diseases such as smallpox and health hazards that once dominated everyday life but are now nearly forgotten. While the introduction of MenAfriVac and its early success is incredibly promising, researchers and public health officials now have the challenging task of monitoring the impact of the vaccine and evaluating its effects on the population. My hope is that the NIH-funded MAP Study will contribute to our knowledge about the immune response following vaccination, and help determine the best strategy for utilising this groundbreaking vaccine to protect those at highest risk in the future.

*Nicole Basta (Gates-Cambridge 2003-2004 – MPhil Epidemiology) is an Associate Research Scholar at Princeton University in the Department of Ecology and Evolutionary Biology. She is the Principal Investigator for the upcoming NIH-MAP study. Additional details of her research can be found at: www.princeton.edu/~nbasta

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