A pinch in the leg, a squeal and a trickle of tears. One baby after another in Malawi is getting the first and only vaccine against malaria, one of history's deadliest and most stubborn of diseases.
The southern African nation is rolling out the shots in an unusual pilot program along with Kenya and Ghana. Unlike established vaccines that offer near-complete protection, this new one is only about 40% effective. But experts say it's worth a try as progress against malaria stalls: Resistance to treatment is growing and the global drop in cases has leveled off.
With the vaccine, the hope is to help small children through the most dangerous period of their lives. Spread by mosquito bites, malaria kills more than 400,000 people every year, two-thirds of them under 5 and most in Africa.
It took three decades of research to develop the new vaccine, which works against the most common and deadly of the five parasite species that cause malaria. The parasite’s complex life cycle is a huge challenge. It changes forms in different stages of infection and is far harder to target than germs.
"We don’t have any vaccines against parasites in routine use. This is uncharted territory,” said Ashley Birkett, who directs PATH’s Malaria Vaccine Initiative, a nonprofit that helped drugmaker GlaxoSmithKline develop the shot, brand-named Mosquirix.
The bite of an infected mosquito sends immature parasites called sporozoites into the bloodstream. If they reach the liver, they’ll mature and multiply before spewing back into the blood to cause malaria’s debilitating symptoms. At that point, treatment requires medicines that kill the parasites.
Mosquirix uses a piece of the parasite - a protein found only on sporozoites’ surface - in hopes of blocking the liver stage of infection. When a vaccinated child is bitten, the immune system should recognize the parasite and start making antibodies against it.
Scientists also are searching for next-generation alternatives. In the pipeline is an experimental vaccine made of whole malaria parasites dissected from mosquitoes’ salivary glands but weakened so they won’t make people sick. Sanaria Inc. has been testing its vaccine in adults, and is planning a large, late-stage study in Equatorial Guinea’s Bioko Island.
And the U.S. National Institutes of Health soon will start initial tests of whether injecting people periodically with lab-made antibodies, rather than depending on the immune system to make them, could offer temporary protection during malaria season. Think of them as "potentially short-term vaccines,” NIH’s Dr. Robert Seder told a recent meeting of the American Society of Tropical Medicine and Hygiene.
For now, only babies in parts of Malawi, Kenya and Ghana are eligible for the Mosquirix vaccine. After the vaccine was approved in 2015, the World Health Organization said it first wanted a pilot roll-out to see how well it worked in a few countries - in real-world conditions - before recommending that the vaccine be given more widely across Africa.
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