There is both less and more than meets the eye in the recent news that an experimental malaria vaccine cut in half the risk that children would contract the illness.
Many of the headlines that followed promised a life-saving vaccine around the corner -- a prospect that in truth remains a maybe. At the same time, the trial results affirmed the benefits of a multipronged attack on malaria.
Each year, about 225 million people are infected by malaria parasites through mosquito bites. Some 781,000 die. Of those, 91 percent live in Africa and 85 percent are under the age of 5.
The death toll has declined in recent years -- from 985,000 in 2000 -- because of enormous anti-malaria efforts by, among others, the Bill & Melinda Gates Foundation and the Global Fund to Fight AIDS, Tuberculosis and Malaria. Measures they have taken include spraying for mosquitoes, distributing insecticide-infused bed nets and treating malaria with the latest, most effective therapies.
A malaria vaccine could be a powerful new tool. Devising one is a steep challenge, however: No vaccine has ever been licensed against a human parasite. Whereas a virus might have a dozen genes, the malaria-causing Plasmodium parasite has more than 5,000 genes and thus many ways to escape the mechanisms of a vaccine, or a drug.
In early trials, the candidate vaccine -- called RTS,S -- proved promising. The recently announced results are from a late-stage study in 15,000 children in seven African countries. Among the first 6,000 children ages 5 to 17 months when they enrolled in the trial, RTS,S reduced clinical malaria, which causes fever and chills, by 56 percent in the first year of follow-up. It decreased severe malaria, which can damage the kidneys and brain, by 47 percent.
Results for the first 6,000 infants in the study, signed up at 6 to 12 weeks of age, won’t be available for another year. This age group is the principal target for the vaccine, which ideally would be given along with other early-childhood immunizations. Vital information on whether the vaccine’s effect persists won’t be available until the end of 2014, along with final trial data.
Nevertheless, the World Health Organization announced that if these data are satisfactory and the vaccine would serve public-health goals, it could recommend RTS,S for use as early as 2015.
Price Is Important
The vaccine’s price would largely determine the extent of its use in the poor countries where it’s most needed. The manufacturer, GlaxoSmithKline Biologicals, has said it would not attempt to recoup its research and development expenses ($300 million so far) and would charge buyers only the vaccine’s manufacturing costs plus 5 percent. The company says potential price tags will be based on various demand models and final efficacy results.
Even if inexpensive, a licensed RTS,S could not be expected to conquer malaria on its own, since it presumably would reduce a child’s chance of getting the disease only by half. But the vaccine efficacy study points us toward what else needs to be done.
Consider that, in the trial, the experimental vaccine’s protective effect came in addition to that of other malaria-prevention measures. About 75 percent of the enrolled children used insecticide-treated bed nets and 7 percent were exposed to indoor spraying for mosquitoes. What’s more, the enrolled children were all given effective diagnoses and treatment when they fell ill, so that the number of malaria deaths was kept low.
Controlling mosquitoes and diagnosing malaria remain essential. Among the highest priorities now is to develop new methods to do both. Only one insecticide class -- pyrethroids -- is licensed for treating bed nets, and resistance to this class has been detected in parts of Africa. For spraying indoors, four classes of bug-killer are available, but resistance to all of them has been seen. A new means of managing the disease may emerge from efforts to expose mosquitoes to substances that will make them resistant to the malaria parasite.
As for diagnostics, there is a great need for inexpensive tests that can detect, on the spot, very low parasite densities. Lacking tests, doctors in many poor settings assume any child with a fever has malaria. Accordingly, they often prescribe anti-malarials unnecessarily. Indiscriminate use of these therapies risks accelerating resistance to them.
Compared with the glamorous fields of drug and vaccine research, mosquito control and malaria testing have attracted relatively little investment from donors and companies. Of the $612 million spent on malaria research and development in 2009, mosquito control accounted for 4 percent and diagnostics for 1 percent, according to a 2011 report published by the Program for Appropriate Technology in Health.
Research investments have produced the innovations that brought malaria fighters this far. But the parasite has demonstrated its ability to overcome obstructions, and continuous discovery is a necessity.
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