Malaria kills millions of people annually, many of them children. So
far, the disease has defied scientists who have tried to create a
vaccine against it. But now, there are several vaccines in different
testing phases.
Scientists have theorized for a long time that
a successful malaria vaccine was possible, but making it has proven to
be a more difficult proposition than they thought. Malaria researcher
Christian Loucq says in part that's because malaria is a very complex
disease.
"It has different phases in the human body... when
the mosquito bites, [the malaria parasite] goes to the liver. It stays
in the liver for some time and then infects the blood, and then it is
going to develop at a very high speed and induce all of the symptoms of
disease, the fever and all that we know is malaria."
Loucq
directs the Malaria Vaccine Initiative for the non-governmental health
research organization PATH. Currently, the MVI has two different
vaccines at different levels of the testing process.
One
vaccine is made from a weakened strain of malaria. With other
disease-causing microorganisms, this approach prompts the body to mount
an immune defense, so it recognizes the stronger form of the disease
when a person gets infected and can fight off the infection. But Loucq
says, with malaria, that approach is more complicated. The vaccine
using this technique is only now being tested for safety on volunteers.
"We
are going to inoculate 104 people [with the vaccine], and we're going
to give them four injections. After some time, we're going to have them
bitten by mosquitoes carrying an effective form of the bug. It is, in
fact, a mosquito that can give the disease."
Loucq says once he
and his colleagues determine that this vaccine is safe for people, they
will proceed with further testing. They should know the answer to the
safety question by the end of 2009.
For the second vaccine,
scientists purified part of the malaria parasite and injected that into
subjects. Loucq says, theoretically, people receiving this vaccine
should create immunity to the disease. Testing for this vaccine is much
further along. The researchers already know that it's safe... and
effective.
"We have shown more than 50 percent protection, which
is a tremendous achievement in the field of malaria. And now we are
going to test those data and [see] if the vaccine works in a much
larger population - 16,000 children and infants in 11 sites and seven
countries across Africa. And that is going to go on for up to three
years, to understand how this vaccine works over a longer period of
time, as well."
Loucq says there are many ways to control
malaria now, including bed nets, insecticides and medications. But he
says the disease won't really be eradicated until there's an effective
vaccine against it. And, he says, some day, that will be developed.
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