Last week U.S. scientists with the biotech company, Sanaria, announced a possible breakthrough on an experimental malaria vaccine: an early trial led to a success rate of 80 percent for the two highest doses. Malaria remains one of the world’s worst scourges. In 2010, the World Health Organization reported 219 million documented cases of malaria (millions more likely went undocumented) and estimated that between 660,000 and 1.2 million died of the disease, mostly children in Africa, that year alone. Mortality is not the only impact of the disease, however: experts have long noted circular links between malaria, poverty, and stalled development.
The new vaccine, known as PfSPZ, was created by using live malaria parasites (Plasmodium falciparum) that have been weakened by radiation. Although mosquitoes carry malaria, it’s actually the parasites inside the mosquitoes that cause the disease. Scientists have long known that repeated exposure to malaria could eventually lead to immunity, however the exposure threshold is extremely high. Experts estimate that one would need to be bit by 1,000 parasite-carrying mosquitoes in order to develop immunity.
Sanaria worked with 57 volunteers on the trial, known of whom had previously contracted malaria. For those given four injections of the new vaccine, two-thirds became immune. However, for all of those given five doses achieved immunity. Still, the trial was small: only nine volunteers were given four doses and only six volunteers, five doses.
“They are clearly very early stage trials in small numbers of volunteers, but without question we are extremely encouraged by the results,” Ashley Birkett, from the Path Malaria Vaccine Initiative, told the BBC.
A number of hurdles remain for scaling up the vaccines, however. The vaccine currently requires mosquito dissectors, who have to manually remove parasites. Furthermore, a vaccine that require five doses and must be injected into the vein means high expense and practicality issues, especially for the people most prone to malaria: the rural poor.
However, experts are confident that many of these hurdles can be overcome, either through further work on PfSPZ or other malaria vaccines under development.
Some experts believe that malaria has killed more people in history than any other disease. According to the WHO, malaria kills a child in Africa every minute.
An Anopheles stephensi mosquito sucking blood from a human host. Anopheles stephensi is one of several mosquito species that carry malaria. Photo by: Centers for Disease Control and Prevention.
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