Two thousand kids to
get experimental malaria jab
Largest ever test of malaria
vaccine to begin in Africa.
9 July 2003
Tom Clarke
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Malaria kills one
million people a
year in Africa. |
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© WHO |
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The most advanced test of a vaccine against malaria
ever conducted in children begins in Mozambique next
week.
The hope is that immunization will become a primary
weapon in the fight against malaria, which kills 1
million Africans each year, most of them toddlers and
babies. Currently, drugs - to which resistance is
rapidly developing - and protections like bed nets are
the only ways to control the disease.
Two thousand children under five will take part in
the trial, funded by the Malaria Vaccine Initiative
(MVI), an independent organization based in Rockville,
Maryland, which coordinates international efforts to
develop malaria vaccines, and drug giant
GlaxoSmithKline. "This is the largest malaria vaccine
trial carried out in Africa to date," says Pedro Alonso,
scientific director of the study's base, the Manhiça
Health Research Centre in Mozambique.
Tests with small numbers of volunteers have satisfied
researchers that the candidate vaccine - called RTS,S -
is safe. The next stage, a phase 2 trial, will now ask
whether the vaccine actually prevents malaria in
children. Results should be available in 18 months.
RTS,S consists of a protein found on the surface of
the malaria parasite at the stage when a mosquito's bite
injects it into the human body. It also contains a
fragment of the hepatitis B virus, too little to cause
the disease, but large enough to goad the body's immune
system into recognizing the malaria fragment.
A chemical mix called an adjuvant is the final
ingredient. This tricks the immune system into mounting
a strong immune response to the vaccine, helping it to
remember the crucial parasite protein.
In tests in the Gambia, RTS,S protected up to 71% of
adults from being infected with malaria. If the vaccine
has similar success in children it must then pass
further tests in babies. Those under a year old are
excluded from this trial for safety reasons but are at
the highest risk of dying from malaria.
Chances of success are slim, admits Melinda Moree,
director of the MVI. Only one of 80 current malaria
vaccine concepts is estimated to succeed, she explains:
"We're going to hear more about failures than
successes." But a clinical trial is the only way to find
out what approaches do and don't work. "Even negative
results move us quite a way forward," she says.
That RTS,S is in the most advanced stages of testing
doesn't mean it is the best candidate vaccine. It has
been in development since the 1980s and has the backing
of a large company, says Adrian Hill at the University
of Oxford, UK.
Hill's team is working on a different approach using
modified viruses to carry malaria genes into the body;
initial results are promising1.
Around nine other candidate vaccines are also in safety
trials this year. |
