Malaria Vaccine (finaly!?)

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October 15, 2004

Malaria Vaccine Proves Effective

By DONALD G. McNEIL Jr.

For the first time, researchers say, a vaccine against malaria has

shown that it can save children from infection or death.

The vaccine, tested on thousands of children in Mozambique, was

hardly perfect: It protected them from catching the disease only

about 30 percent of the time and prevented it from becoming

life-threatening only about 58 percent of the time.

But because malaria kills more than a million people a year, 700,000

of them children, even partial protection would be a public health

victory. The disease, caused by a parasite carried by mosquitoes, is

found in 90 countries, and drug-resistant strains are spreading.

Dr. Allan Schapira, strategy coordinator for the Roll Back Malaria

campaign at the World Health Organization, said the trial was " good

news, and definitely of great interest for malaria control. "

The director of the Malaria Vaccine Initiative, which is underwriting

tests on 15 experimental vaccines with money from the Bill and

Melinda Gates Foundation, said the GlaxoKline product tried in

Mozambique was now its leading candidate and had proved that the

concept worked.

" We'd all like to see the numbers be higher, absolutely, " said Dr.

Melinda Moree, director of the initiative. " But these are still very

significant findings. "

The results - to be published tomorrow in the British medical journal

The Lancet - were comparable to or better than other methods of

preventing infection in African villages, like distributing mosquito

nets and insecticides, she said.

A malaria expert not connected with the study, Dr. Dyann Wirth,

director of the Harvard Malaria Initiative, a program at the Harvard

School of Public Health that is also seeking cures, was more

cautious. She said the findings opened " a fruitful area for further

investigation, " but needed larger trials.

Glaxo and the Malaria Vaccine Initiative are planning such trials.

But experts said it would be several years before the vaccine could

be adopted as a childhood inoculation like those for diphtheria or

measles. It is not yet known how long the vaccine's protection lasts,

whether it is safe for infants and whether it is compatible with

other vaccines.

A trial of the same vaccine among adults in Gambia six years ago

showed that it protected about 35 percent of them from infection, but

that the protection waned after about two months.

Still, experts noted that children stand to benefit more from a

vaccine. In rural Africa, people can be infected several times a

year. Children who survive to adulthood become immune. Newborns

inherit some protection from their mothers, but it wears off in a few

months. Young children are the hardest hit, and many who survive are

brain-damaged.

The most recent vaccine test, conducted in two rural districts in

southern Mozambique, where malaria is endemic during the six-month

rainy season, involved 2,022 children ages 1 to 4. Half of them were

given the malaria vaccine; rather than placebos, the other half got

vaccines against hepatitis or bacteria that cause meningitis.

To ensure that the results were not skewed by other factors, the

control and vaccine groups had roughly equal numbers of children who

slept under mosquito nets at home and who lived near a clinic. The

children were followed for six months and had home visits with blood

and temperature checks at least once a month. Those who developed

malaria were given immediate medical attention; the disease can kill

in as little as 48 hours, but it can be cured if it is caught in

time.

To test the vaccine's ability to prevent new infections, two

subgroups of about 180 children each were given drugs to clear any

parasites they might have had before the trial began. In both

subgroups, most children developed new parasites. But the number was

considerably smaller among those who had received the vaccine: 123

children in the vaccine group, compared with 159 in the control

group. Over all, 11 vaccinated children developed severe malaria

while 26 in the control group did.

Fifteen children died of various causes. None in the vaccine group

died of malaria, while four in the control group did. Those numbers

are too small to have any statistical meaning.

Mozambique is one of the world's poorest countries, where 200 out of

every 1,000 children die before age 5, said Dr. Regina Rabinovich,

director of infectious diseases for the Gates foundation, so the

death rate across the whole study was lower than normal, presumably

because the children in it got better than average medical care.

The trial was conducted by the biologicals division at Glaxo and the

Mozambique Ministry of Health, with financing from the Malaria

Vaccine Initiative, which was created in 1999 with $50 million from

the Gates foundation.

Malaria is spreading - possibly, some experts say, because global

warming has encouraged the spread of mosquitoes. More people die of

the disease today than did 30 years ago.

Beyond death and retardation, there are economic consequences. For

example, families affected by malaria harvest only 40 percent of the

crops of healthy ones, according to the World Health Organization.

A malaria vaccine, one of the holy grails of tropical medicine, has

proved surprisingly elusive. Health authorities have been fighting

malaria since the Panama Canal was a gleam in Theodore Roosevelt's

eye.

Until the Gates foundation arrived, work on vaccines for tropical

diseases had languished for decades because they make little profit

for drug companies. (The world spends about $400 billion a year on

drugs, but only about $8 billion on vaccines.) The American military,

which also does malaria research, had limited amounts of money for

it.

The Glaxo vaccine, known as RTS,S/AS02A, has been in development and

testing for 17 years, said Dr. Joe Cohen, one of its inventors. It

fuses a bit of hepatitis B virus with a bit of the falciparum strain

of the parasite, which is the most common, and usually the most

deadly, form of malaria. The piece of the parasite is from the life

stage that is injected by mosquitoes, so antibodies and white blood

cells stimulated by the vaccine attack before the parasite can settle

in the liver and reproduce.

Pieces of the hepatitis virus were added because they provoke strong

immune responses, Dr. Cohen said. (Another malaria vaccine candidate

uses a weakened version of a smallpox vaccine to do the same.)

The goal, he said, is to create immunity that lasts longer than

natural immunity, which fades in adults after they move out of

malaria areas.

Dr. Rabinovich of the Gates foundation said future vaccines might

incorporate proteins from other parts of the parasite's life cycle.

But she added: " This demonstrates that vaccines have the potential to

prevent millions of child deaths. That's something to wake your mom

up about. "

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