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Experimental Malaria Vaccine Shows Promise in Africa

December 11, 2007 at 6:25 PM EDT
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Malaria kills one African child about every 30 seconds. Now, a vaccine developed by GlaxoSmithKline and the Bill and Melinda Gates Foundation shows promise in reducing the rate of severe malaria by as much as 50 percent. Susan Dentzer reports from Tanzania.

JIM LEHRER: Now, the promise of a new malaria vaccine. Susan Dentzer of our Health Unit reports from Tanzania on the eastern coast of Africa. Our unit is a partnership with the Robert Wood Johnson Foundation.

SUSAN DENTZER, NewsHour Health Correspondent: It’s beautiful here in Bagamoyo on Tanzania’s north eastern coast, but Nia Ramadhani Suma who lives here has plenty of reason to worry. Her daughter, Salma Othman, is just weeks old in a part of the world where five million children under 5 die every year.

A major cause of these premature deaths is something almost no Americans ever encounter: the mosquito-borne ravages of malaria. The disease kills one African child about every 30 seconds.

And that’s why this Tanzanian mother chose to have her baby injected with an experimental malaria vaccine. Salma Othman is one of hundreds of African babies now participating in clinical trials to test this vaccine, called RTS,S. Both her mother and father, Kais Mohammed Othman, are enthusiastic.

NIA RAMADHANI SUMA, Tanzanian Mother (through translator): I learned about this malaria vaccine from a friend. She participated in an earlier study and encouraged me to enroll Salma.

KAIS MOHAMMED OTHMAN, Tanzanian Father (through translator): I’d like to see Salma spared from having malaria in the future. I hope that the vaccine will succeed and it will one day be used for all children in Africa.

SUSAN DENTZER: It’s a truly historic moment. Never before has a malaria vaccine shown this much effectiveness in babies and young children, nor made it this far in the testing process.

Early studies suggest the vaccine can cut malaria infections in infants and young children by as much as 65 percent. Next year, an even broader testing phase will try to confirm the earlier results in trials involving up to 16,000 children in seven African countries.

The vaccine is a product of several hundred million dollars worth of research over the last quarter-century. It’s being produced under a partnership between the global pharmaceutical company GlaxoSmithKline and the PATH Malaria Vaccine Initiative. That’s a nonprofit effort funded largely by the Bill and Melinda Gates Foundation.

ANDREW KITUA, Tanzania National Institute for Medical Research: They would like the malaria vaccine to be there yesterday.

SUSAN DENTZER: Dr. Andrew Kitua, director of the Tanzanian government’s National Institute of Medical Research, told us why he and other health officials throughout Africa are so hopeful about the vaccine.

ANDREW KITUA: Malaria in Tanzania is the number-one priority health problem. It affects practically the spectrum of all the populations and all the age groups. Although the most severely affected are children under the age of 5 and pregnant women.

Economic and physical effects

SUSAN DENTZER: Kitua says so many are frequently sickened by the disease that it's been estimated to cost the worst-affected nations billions of dollars a year in lost economic growth.

ANDREW KITUA: Most of the people who are in malaria-endemic areas are affected three or four times a year, so all those are days that are cut off from the normal production activity at the household.

SUSAN DENTZER: Muhammad Kais Othman, Salma's father, told us he was a case in point.

KAIS MOHAMMED OTHMAN (through translator): I can't remember how many times in my life I've had malaria. I had it last May, and it gave me a headache, weakness and vomiting. Usually I work as a carpenter and I repair bicycles, but when I was sick I couldn't do anything. I lost income. I could only work for two hours a day, and then I had to stop.

SUSAN DENTZER: The cause of malaria is a parasite carried by the female Anopheles mosquito in its salivary glands. When the mosquito bites a human, the parasite travels through that person's bloodstream into the liver.

Dr. Ricky Ballou of GlaxoSmithKline, who oversees this vaccine program for the company, told us what happens next.

DR. RIPLEY BALLOU, GlaxoSmithKline: The number of organisms that are actually deposited by the mosquito is relatively small, maybe a few hundred. But once it's in the body, it begins to multiply. And over a relatively short period of time, a week or two, you can end up with literally billions of these parasites in your bloodstream.

SUSAN DENTZER: The result is malaria and the fever, chills, headaches and muscle aches that even a mild case can bring. In severe malaria, the presence of billions of parasites in the blood, clearly visible under a microscope, can cause extreme anemia. They can also interfere with the functioning of organs like the kidneys, brain and lung, and lead to a gruesome death.

We saw the effects up close at the Bagamoyo district hospital, where 3-year-old Jafari Juma (ph) was recovering from his second bout of malaria. Dr. Salim Abdulla, a doctor and also a scientist involved in the vaccine trials, explained.

DR. SALIM ABDULLA, Ifakara Health Research and Development Center: He come in with a very high fever and also abdominal pains. So we checked his blood, and we found out that he had over 250,000 parasites per microliter of blood. And this clearly indicated that Jafari (ph) was seriously sick and could succumb any time.

SUSAN DENTZER: After three days of treatment with quinine, the standard therapy here in Tanzania, Juma (ph) was recovering. His mother told Dr. Abdulla that another son at home, age 2, had already had several bouts of malaria, as well.

Even if young children like this don't die from these episodes, they face long-term effects that can even harm their cognitive developments, says Dr. Kitua.

ANDREW KITUA: They may have repeated episodes, which don't into very severe episodes, but then keep them constantly anemic. They're not concentrating in school as they would have been expected if malaria was not an issue.

Boosting immune response

SUSAN DENTZER: Fortunately, African countries like Tanzania have already begun to make inroads into curbing malaria through various measures. These include spraying insecticide to combat mosquitoes and the use of insecticide-treated bed nets.

But a vaccine would clearly add a critical new weapon to this arsenal. As with all vaccines, it would mobilize the body's immune system to fight infections, if other protective measures failed. Up until now, that's proved to be a challenge that no previous malaria vaccine candidate has been able to meet, says Dr. Ballou.

DR. RIPLEY BALLOU: Parasites by definition have learned to live with the human host. And, therefore, they have many tricks that they use to deflect our immune system so that we don't get rid of them.

In the case of the malaria parasite -- and I'll use an analogy here from "Star Trek" -- a sort of cloaking device, a biological stealth protein that coats the parasite and which essentially shields the parasite from the immune system of the child.

SUSAN DENTZER: So the researchers who developed the vaccine took a piece of this stealth protein, chemically manipulated it, and added in a special immune system booster. Once the vaccine is injected, the body produces two types of immune cells, antibodies and so-called t-cells that kill the parasites before they've multiplied wildly.

Tested several years ago in children ages 1 to 4 in Mozambique, the vaccine produced surprisingly good results.

DR. RIPLEY BALLOU: We were able to cut the rate of clinical malaria by 35 percent, and that effect lasted for at least 18 months. But even more importantly, when we looked at the rate of severe malaria -- and this is the form of the disease that can kill children -- we were able to cut the rate of severe malaria by as much as 50 percent. And, again, that was sustained over at least 18 months.

Involving the global community

SUSAN DENTZER: In a larger clinical trial scheduled to begin next year, babies will be divided into two groups. One will get the malaria vaccine in three separate doses over the course of seven months. Instead of a placebo, the other group will get a vaccine such as one against Hepatitis B, valuable for protecting kids in Africa from the ravages of that disease.

Babies will be injected when they're brought to clinics to receive the standard battery of childhood vaccines now given throughout Africa. Ballou says that the earliest results could be in by the end of 2010.

If they show the vaccine works as well as expected, the hard part will follow: getting the vaccine to as many as 50 million children a year in desperately poor countries.

DR. RIPLEY BALLOU: Once those data are available and if they are, as we expect them to be, very positive and promising data, we want to make this vaccine available to children in Africa wherever they are, as quickly as possible.

And this is going to be something that is going to require hard work, not only on the part of the company, but of the global health community to really tackle this serious problem of malaria.

SUSAN DENTZER: Under arrangements that will have to be negotiated with global health authorities, GlaxoSmithKline expects that it will be reimbursed for its manufacturing costs, but those funds and other monies for distributing the vaccine will have to come mainly from the world's wealthy nations.

A last look at baby Salma and her parents showed why for this family, as for so many throughout Africa, the stakes are so high.