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An experimental malaria vaccine only protects about a third of children from malaria over four years, but it could still save millions of lives, researchers reported Thursday.
It’s the final report on the vaccine called RTS,S/AS01, the only vaccine that’s been shown to protect at all against malaria.
The news isn’t great, and researchers were puzzled by some of what they found.
They tried giving booster doses of the vaccine to see if they could improve how well it worked. But even three doses protected only 36 percent of the kids after four years – down from 50 percent protection in the first year,” the team, led by Brian Greenwood of the London School of Hygiene & Tropical Medicine, wrote in the Lancet medical journal.
“The new results show that, with a booster of the vaccine, the overall efficacy against severe malaria in 5 to 17-month-old children was 32.2 percent,” Vasee Moorthy and Jean-Marie Okwo-Bele of the World Health Organization wrote in an accompanying commentary.
“Because the vaccine’s efficacy is so short-lived, as expected a booster dose is shown to be of some value but it was not as effective at the initial doses,” said Adrian Hill, Director of Jenner Institute at Britain’s University of Oxford.
“More worrying is the new evidence of a rebound in malaria susceptibility: after 20 months vaccinated children who were not boosted showed an increased risk of severe malaria over the next 27 months compared to non-vaccinated controls.”
It’s possible the vaccine provides limited immunity and that when it wears off, the children are more susceptible than before, the researchers said.
Nonetheless, the researchers said careful use of malaria vaccines could save millions of lives.
"Given that there were an estimated 198 million malaria cases in 2013, this level of efficacy potentially translates into millions of cases of malaria in children being prevented."
“Given that there were an estimated 198 million malaria cases in 2013, this level of efficacy potentially translates into millions of cases of malaria in children being prevented,” Greenwood said.
According to the WHO, more than 580,000 people died of malaria in 2013, mostly children under the age of 5.
The mosquito-borne disease is hard to fight because it’s caused by a parasite, not by a germ. The little Plasmodium falciparum creature lives in the blood and the liver and it’s hard to target. Vaccine makers have been trying for decades.
“It has taken 20 years to get here and, while the levels of protection the vaccine offers against clinical malaria may seem relatively low, they are better than any other potential vaccine we currently have,” said Mike Turner, Head of Infection at Britain’s Wellcome Trust.
The World Health Organization will be deciding whether to buy and distribute malaria vaccines later this year. Other tools against malaria include insecticides and bed nets.
In a second report, researchers said malaria may have killed as many people in West Africa as the Ebola epidemic has.
They said the disruption to bed net and treatment programs caused by the epidemic may have led to the deaths of 10,900 more people from malaria than otherwise would have occurred. And there were probably 3.5 million more cases of malaria because of the disruption, they wrote in Lancet Infectious Diseases.