Researchers at the Yale School of Public Health have found that an alternative meningitis vaccination strategy in Africa may save more lives at a lower cost.
The Yale-led team created a mathematical model to weigh the relative costs and benefits of different strategies for distributing a meningitis vaccine that is currently being developed, publishing their results on Jan. 24 in the journal PLOS Medicine.
“Models can be an important tool in understanding these dynamics,” said Caroline Colijn, co-author of the study. “We can’t do experiments, because the effects are on people, take place over long time periods and are rooted in population-level effects that you can’t see in a small sub-population.”
Under current World Health Organization recommendations, the meningitis vaccine would be given out in reaction to an outbreak in a given district, said Reza Yaesoubi, professor of public health and the study’s lead author. However, as the cost of the vaccine has decreased and its length of effectiveness increased, there has been a push to reconsider how vaccination is implemented in countries such as Burkina Faso, the nation studied in the paper. The researchers found that a nationwide immunization campaign targeting school-aged children would be the most cost-effective solution.
“We wished to study whether we could simply do away with these reactive campaigns by getting rid of the disease up front,” said Marc LaForce, study co-author and former director of the Meningitis Vaccine Project, adding that the group had done a “magnificent job” in modelling the potential implementations of the vaccine.
Although the vaccine currently used is effective against the predominant strain of meningitis, LaForce is working to create a more comprehensive vaccine that will address five more circulating strains of meningitis in Africa and be ready for implementation around 2020–21. At that point, the World Health Organization will formulate a set of recommendations on how the vaccine should be used. LaForce’s team approached the Yale epidemiologists to create a model that would serve to inform policymakers as to what the most effective vaccination strategy would be.
The researchers found that the most cost-effective strategy for vaccination targets children aged one to 18. Many of these children attend school, which makes them easier than older age cohorts to find and vaccinate, Yaesoubi said. The vaccination of these children, who are at especially high risk for the disease, will lead to herd immunity that will significantly decrease the risk of an outbreak in the region.
Burkina Faso is one of the countries situated in the meningitis belt, a group of sub-Saharan African countries especially susceptible to meningococcal epidemics, which routinely devastate their populations, LaForce said. Between 2001 and 2010, a vaccine was developed to treat the predominant strain of meningitis in Africa and has thus far been very successful; however, he added, other strains of meningitis have continued to circulate.
The current reactive strategy for vaccination makes intuitive sense when considering the financial constraints under which many nations in the meningitis belt are operating, Yaesoubi said. When a meningitis outbreak occurs in a certain district, health professionals enter that district and vaccinate the population there. However, there is often a significant time-lag between the onset of an epidemic and the implementation of the vaccine, leading to death and spread of the disease in the interim, said Ted Cohen, professor of epidemiology at the School of Public Health and senior author of the study.
It was only when the researchers began to work on their comprehensive mathematical model — which accounts for factors including the predicted spread of the virus and the role of herd immunity — that they were able to characterize the impact of various immunization strategies, Cohen said. The sporadic nature of meningococcal outbreaks made the creation of the model particularly challenging, but the team is confident that it has successfully calibrated its model to account for the disease’s many features, he added.
According to Yaesoubi, now that this work has been published, the team plans to turn its attention to studying meningitis in Niger, a nation that is also located in the meningitis belt.
Since 2010, more than 280 million people in 21 African meningitis belt countries have been vaccinated against Meningitis A, the predominant form of the disease in the region, through a series of vaccination campaigns, according to the World Health Organization.
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