“After over four decades of malaria vaccine research, we have reached a new stage,” says Vasee Moorthy, who works on malaria vaccines at the World Health Organization (WHO) in Geneva. Vaccination with RTS,S showed a 54% reduction in clinical malaria cases, and a 47% reduction in severe malaria cases, in 6,000 children aged 5–17 months compared with controls. More data from this large-scale trial, conducted on 15,460 children in total, across 11 sites in seven African countries will emerge over the next 3 years, and barring any major setbacks, the vaccine could be licensed for use in Africa as early as 2015. “Scientifically, this is startling. Few believed that with one protein of a very complex parasite you would be able to make a vaccine that protects at the level that this does,” says Melinda Moree, CEO of Washington, DC–based BIO Ventures for Global Health, and former director of the PATH Malaria Vaccine Initiative (MVI).
Recent efforts to control malaria—including the introduction of insecticide-treated bed nets and drugs such as artemisinin (see p. 1072)—have helped control the disease. Yet despite their success, nearly 800,000 people continue to die of the disease each year, most of them children in Africa under 5 years of age. Since the 1970s, several vaccine candidates have come and gone, thwarted by a parasite that is no ordinary foe. The Plasmodium parasite that causes malaria has around 5,000 genes, far more complex than a virus or bacterium, and it is unusual in having three stages in its life cycle, changing its form as it progresses through liver (or pre-erythrocytic) and blood stages in humans, as well as in a third stage that occurs in the mosquito gut. “To be frank, it's very hard to make a vaccine that is 90% or 100% effective against any of these stages, as we've discovered,” says Adrian Hill, director of the Jenner Institute in Oxford, UK.
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