Malaria vaccine helps small children

In trials in Mozambique, medicine reduced cases of illness and its severity

October 15, 2004|By Thomas H. Maugh II | Thomas H. Maugh II,LOS ANGELES TIMES

After more than two decades of research, researchers said yesterday that they have found the first vaccine that is effective against malaria.

Trials in Africa showed that the vaccine blocked almost half of new infections in young children and reduced serious disease by nearly 60 percent.

Experts termed the results a major breakthrough in efforts to tame a disease that afflicts 400 million people each year, killing 1 million to 3 million - most of them children in Africa. Malaria is the leading killer of children under age 5 and ranks with AIDS and tuberculosis among the world's most lethal diseases.

Researchers are not sure how long the vaccine's protection will persist, but even a partially effective vaccine will have great value in fighting a disease that is becoming increasingly resistant to the drugs most commonly used to treat it.

More trials are needed to confirm the vaccine's efficacy, particularly in the youngest children, who are most likely to die from infections. But it could be available for widespread use by 2010, experts said.

By that time, the World Health Organization predicts, half the world's population will be living in areas of high exposure to the disease, compared with 41 percent now.

Breaking the cycle

Other potential malaria vaccines have been tested "but we have never seen results like this before," said Dr. Pedro Alonso of the University of Barcelona, who headed the trial reported this week in the journal Lancet.

The vaccine could make a major contribution to "breaking the cycle of disease and poverty that so badly affects sub-Saharan African countries," Alonso said.

Producing a malaria vaccine is considered the most urgent goal in controlling the disease, because it offers the safest, least expensive method. Antimalarial drugs such as Larium, known generically as mefloquine, can be used to prevent infection by killing the parasite, but they are much more expensive, require regular use and can produce many undesirable side effects.

Developing a vaccine has been difficult because the disease is produced by a parasite with a complicated life cycle. Science has yet to come up with an effective vaccine against a parasite, said Melinda Moree, director of the Malaria Vaccine Initiative.

Carried by mosquitoes

Malaria is caused by four closely related parasite strains, the most common and deadly of which is Plasmodium falciparum. The strains thrive in Anopheles mosquitoes.

The life cycle begins when infected mosquitoes bite humans, injecting them with the form of the parasite called sporozoites. These invade the liver and begin reproducing in a new form, called merozoites.

Some merozoites can remain dormant in the liver for years, but most escape into the bloodstream and infect red blood cells, where they continue to replicate. Eventually, the blood cells burst, releasing more of the parasite into the bloodstream. This causes most of the symptoms associated with malaria.

The parasites are then ingested by mosquitoes when they bite an infected human. These reproduce in the mosquito's gut and start the cycle all over again when the mosquito bites an uninfected person.

The new vaccine, called RTS,S/AS02A, was developed by GlaxoSmithKline Biologicals.

The trial involved more than 2,000 healthy children ages 1 to 4 living in Manhica, a district in rural southern Mozambique.

The Los Angeles Times is a Tribune Publishing newspaper.

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