Heavy
Blow To World's First Mass AIDS Vaccine Trial
2-24-3
- The outcome of the world's first AIDS vaccine to
undergo mass trials on humans dealt a heavy blow to campaigners hoping
for a shield against the global pandemic.
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- Tested over three years, AIDSVAX failed to protect
most volunteers against HIV infection but did apparently have some
protective effect on blacks and Asians, its makers, VaxGen Inc.,
announced on Monday.
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- The trial "did not show a statistically significant
reduction of HIV infection within the study population as a whole, which
was the primary endpoint of the trial," it admitted.
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- The vaccine or a dummy lookalike were administered in
three doses to 5,009 volunteers, primarily gay men in the United States,
as well as volunteers in Canada, Puerto Rico and the Netherlands.
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- Two-thirds were given the vaccine, and one-third the
placebo.
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- The northern California biotech company said there was
a "statistically significant" reduction of HIV infection amongst blacks
and Asians.
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- "There were 67 percent fewer HIV infections among
ethnic minorities, other than Hispanic individuals," the company said
Monday.
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- "There were 78 percent fewer HIV infections among
black volunteers who received vaccine compared to placebo
recipients."
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- Phillip Berman, VaxGen's senior vice president of
Research and Development and inventor of the vaccine, said that those
results were heartening.
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- They showed "certain groups have a better immune
response" to HIV and this warranted further study, he argued.
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- However, that contention was questioned by the
International AIDS Vaccine Initiative (IAVI), a New York-based
organisation that is pushing hard to promote a vaccine against the human
immunodeficiency virus (HIV).
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- It said the number of infections among ethnic
volunteers was too small to draw any firm conclusion.
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- There were only 13 infections among black volunteers,
four in the vaccine group and nine in the placebo group.
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- In addition all the volunteers received counselling on
safe sex, a factor known by scientists to affect infection rates.
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- "The news on VaxGen's AIDSVAX is disappointing, but we
are not discouraged," IAVI president Seth Berkley said. "The search for
an AIDS vaccine will -- and must -- go on.
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- "A vaccine is the world's best hope to end the spread
of a virus that infects nearly 15,000 men, women and children daily and
threatens the survival of whole communities."
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- Peter Piot, executive director of the UN agency
UNAIDS, said some of the results were "promising".
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- "The trial provides clear evidence that a vaccine can
work. However, there is an urgent need for more targeted research to
find out why the candidate vaccine only seems to work in certain
population sub-groups."
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- AIDSVAX is the only vaccine to have been tested
through all three phases of medical trials -- a long, arduous and
expensive process for assessing safety and effectiveness that takes a
candidate medicine out of the laboratory and into the public
domain.
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- The trial vaccine is based on priming antibodies, the
first line of the body's defence.
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- Its goal is to get the antibodies to identity the
so-called gp120 protein on the surface of HIV which enables the virus to
dock with an immune-system cell, the first stage before penetrating
it.
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- Although lab tests had shown that gp120 antibodies
could be stimulated, there had already been some evidence to cast doubt
on whether the response has the punch to destroy the virus.
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- Disappointment with antibodies has prompted many AIDS
vaccine researchers to try another tack, switching away from antibodies
and towards cellular immunity: getting killer lymphocytes to recognise
and destroy cells already infected by HIV.
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- This would not, however, destroy virus in the
bloodstream, which means it could still infect other people through, for
instance, shared drug syringes.
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- A senior European researcher said the results from
this first-generation vaccine were a "disappointment" but "not a
surprise."
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- "We have known since the beginning that antibody-based
vaccine strategies will not be enough to fight the incredible diversity
of this virus," said Jean-Gerard Guillet, head of the preventive vaccine
programme at ANRS, France's National AIDS Research Agency.
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- Guillet added, however, that knowledge could only
progress through the concrete results of mass trials.
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- He put the typical cost of a Phase III trial at more
than 70 million dollars.
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- A Phase III trial of AIDSVAX is also underway among
injection drug users in Thailand, testing a formulation that is designed
to protect against the HIV subtypes B, which is prevalent in North
America and Europe, and E, which is prevalent in central Africa and
Southeast and East Asia.
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- According to UN figures, around 20 million people have
already died from acquired immune deficiency syndrome (AIDS) and another
42 million people had HIV or AIDS in 2002.
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