Experimental Malaria Vaccine Slashes Infection Risk By Half

Oct 18, 2011
Originally published on October 18, 2011 5:33 pm

After decades of disappointment, researchers think they're finally on track to unleash the first practical vaccine against malaria, one of mankind's ancient scourges.

In the world's first large field trial of an experimental malaria vaccine, several thousand young children who got three doses had about 55 percent less risk of getting the disease over a year than those who got a control vaccine against rabies or meningitis.

Dr. Christian Louqc, who's leading the final-phase clinical trial at 11 sites across Africa, tells Shots that among several thousand children who got "control" vaccines, there were 1,500 cases of malaria — more than one episode per child in the following year. But for every 1,000 children who got the experimental malaria vaccine, there were only 750 cases of malaria.

Considering only life-threatening malaria, there were 20 cases among every 1,000 children who got the study vaccine, compared to 40 cases per 1,000 children who got vaccines for other diseases.

Researchers say adverse reactions occurred equally among children who got the malaria vaccine and those who got control vaccines. Some children who got the malaria vaccine had fevers and seizures, but all recovered. There was also a higher incidence of meningitis among those vaccinated against malaria, but the researchers don't think the cases were caused by the vaccine.

Of course, 50 percent effectiveness is far less than the 90 percent-plus protection offered by established vaccines against polio, measles, whooping cough, tetanus and other infections.

When asked if the Bill and Melinda Gates Foundation, which funded much of the malaria vaccine development, considered the 50 percent effectiveness level satisfactory, the foundation's Dr. Regina Rabinovich said, "I would prefer to see 100 percent efficacy, absolutely." She said more data will be needed to determine if the results are strong enough to warrant deploying the vaccine widely.

Still, as a first step, malaria researchers say the new vaccine could prevent malaria in tens of millions of children and save hundreds of thousands of lives per year. Malaria relies on mosquito bites of infected humans to spread. And one infected person in a community can lead to 100 other cases.

"We are very, very happy," Loucq told Shots. "It's the first vaccine developed against a parasite. Developing a vaccine against a parasite is not an easy task."

The decade-long development of this vaccine, termed RTS,S for its different components, has so far consumed more than a half-billion dollars – about $300 million from its sponsor, GlaxoSmithKline, and $200 million from the Gates Foundation, through grants to a nonprofit group called the PATH Malaria Vaccine Initiative. Loucq is head of the MVI.

Dr. Patricia Njuguna, a Kenyan pediatrician in charge of one of study sites, told Shots that when the results became clear last month, "the response was quite a lot of relief because it actually confirmed that what we'd been seeing previously was not a fluke result, it was really the real thing."

"We were absolutely thrilled," says Dr. Ripley Ballou of GlaxoSmithKline. "It's what every vaccine developer dreams of — being able to work on a project like this."

Since malaria kills nearly 800,000 people a year — most of them children under 5 in sub-Saharan Africa — the impact of a vaccine that's 50 percent protective could be large, if the economics and logistics of deploying it can be worked out.

"When you multiply this across all the small villages, the countries, the communities now living under this threat, it's a huge issue," Ballou told Shots.

The study, released at a malaria conference in Seattle and published online by the New England Journal of Medicine, involved 6,000 children 5 to 17 months old. They were scattered among seven sub-Saharan African countries — a region where malaria sickens tens of millions every year.

The vaccine news comes at a time when optimism about controlling malaria is rising. The World Health Organization's Roll Back Malaria program reported yesterday at the Seattle meeting that up to a third of the 108 countries where malaria is endemic are close to being able to eradicate malaria.

This has been achieved through the use of modern diagnostic tests and effective treatment, deployment of insecticide-impregnated bed nets to reduce bites from infected mosquitoes, and insecticide spraying of homes.

Deaths from malaria worldwide have declined 20 percent over the past five years or so.

By validating earlier, smaller studies, the new trial is encouraging public health experts to think again about eradicating malaria. An earlier campaign to stamp out the disease in the 1950s made significant inroads. But it foundered as the malaria parasite developed resistance to the mainstay treatment, a drug called chloroquine, and Anopheles mosquitoes became resistant to the insecticide DDT.

A year from now researchers expect to release results on about 9,000 younger infants — those six to 12 weeks old. They represent the primary target population to get a malaria vaccine along with other immunizations.

Advocates say this week's results put the malaria vaccine on track to win approval in 2015 from the European Medicines Agency and from World Health Organization.

It's not yet clear how much the vaccine will cost. "We have no intention of making a profit here," GlaxoSmithKline chief executive Andrew Witty said at a teleconference Tuesday. "We are committed to achieving the lowest price possible."

GSK has committed to charging no more than the cost of producing the vaccine plus a 5 percent margin that will be devoted to malaria treatment and other infectious disease research. Witte says GSK will press its suppliers "to commit to reducing their profit margins or eliminating profit altogether," and adds that the company may locate malaria vaccine plants in Africa or India "as a further means to reduce the cost."

But GSK officials wouldn't comment on the possible price range. UNICEF buys many vaccines for pennies a dose. For instance, polio vaccine costs the agency about 15 cents a dose, hepatitis B costs 18 to 40 cents a dose, and meningitis costs 85 cents to $1.04.

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This is ALL THINGS CONSIDERED from NPR News. I'm Robert Siegel.


And I'm Melissa Block. First this hour, a landmark in public health. Researchers say they have solid evidence that an experimental vaccine against malaria works. A study of 6,000 children across Africa shows the vaccine cuts the chances of getting malaria by more than half. As NPR's Richard Knox reports, the results are fueling talk of eradicating a disease that kills hundreds of thousands of people each year.

RICHARD KNOX, BYLINE: This is the first time malaria vaccine developers can really claim they're onto something that might make a difference. Dr. Tsiri Agbenyega of Ghana, one of 140 authors of today's study, spoke about the results at a big malaria conference in Seattle.

DR. TSIRI AGBENYEGA: This is remarkable when you consider that there has never been a successful vaccine against a human parasite, nor obviously against malaria.

KNOX: It's hard enough to make a good vaccine against the bacterium or a virus. Those are simple targets compared to the malaria parasite. It morphs into many different forms as it cycles from mosquitoes to humans and back again. And surviving malaria doesn't mean you can't get it again. In the study, researchers found that kids who didn't get the vaccine got malaria on average one and a half times a year. In fact, for every 1,000 kids who did not get the new vaccine, there were 1,500 cases of malaria.

DR. CHRISTIAN LOUCQ: If those kids had received the vaccine, those kids had only 750 cases of malaria, a reduction by half.

KNOX: That's Dr. Christian Loucq of PATH Malaria Vaccine Initiative. He led the new study, which is published online by the New England Journal of Medicine. Loucq says the vaccine also cut the risk of the most serious cases of malaria.

LOUCQ: So that means in fact we reduce the chances to die from malaria by half.

KNOX: But a vaccine that cuts the risk of sickness and death by half is much less effective than vaccines against polio, measles, pneumonia or other diseases. They typically prevent infection around 90 percent of the time. One official at the Bill and Melinda Gates Foundation, which has put $200 million into the new vaccine, said she didn't know if it will be considered good enough to give to hundreds of millions of children. But authors of the new study were less cautious.

DR. PATRICIA NJUGUNA: I think most parents would be happy to have 50 percent less cases.

KNOX: That's Dr. Patricia Njuguna, a Kenyan researcher.

NJUGUNA: So if you can even reduce the multiple episodes in that child to one or none, that would be a big relief to a mother rather than having multiple episodes of malaria.

KNOX: And others point out that malaria is such a big problem that a less-than-ideal vaccine could still make a huge difference. Half the world's population is threatened by malaria. Nearly a quarter of a billion people get infected every year, and almost 800,000 die, most of them children under 5 in Africa. But the decision on whether to launch a malaria vaccine is complicated. Nobody knows how long its protection will last or how much it will cost. Most vaccines for the developing world cost pennies a dose. One of the most expensive, for pneumonia, costs three-and-a-half dollars a dose. Dr. Andrew Witty, head of GlaxoSmithKline, told reporters today that the company will keep this vaccine affordable.

DR. ANDREW WITTY: Our intention is to supply this vaccine at the lowest price possible. We have no intention of making a profit here.

KNOX: The new vaccine comes at a time of optimism about rolling back malaria. Deaths have already been cut by 20 percent over the past few years. Professor Dyann Wirth of Harvard says this has been accomplished with relatively low-tech measures - bed nets to keep mosquitoes from biting, insecticide sprays, prompt diagnosis and treatment.

DR. DYANN WIRTH: If you were keeping score, you know, malaria, public health community, well, I would say malaria is still winning, but there are some battles where actually the public health community is doing better than it was previously.

KNOX: Some are saying that adding even a partially effective vaccine could make eradication of malaria possible. Bill and Melinda Gates proposed that back in 2007.

WIRTH: In their lifetime, it's possible. I mean, we're thinking this is a 40- or 50-year task.

KNOX: That would put it around the year 2060. Richard Knox, NPR News. Transcript provided by NPR, Copyright NPR.