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HIPPOLYTE BWIZA MUHIRE [ Profil ] |
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New Vaccine couldHelp Prevent HIV Infection
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Oct 1st, 2009 - 11:22:17 |
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For the first time, an experimental vaccine has prevented infection with the
AIDS virus, a watershed event in the deadly epidemic and a surprising
result. Recent failures led many scientists to think such a vaccine might
never be possible.
The World Health Organization and the U.N. agency UNAIDS said the results
"instilled new hope" in the field of HIV vaccine research.
The vaccine -- a combination of two previously unsuccessful vaccines -- cut
the risk of becoming infected with HIV by more than 31 percent in the
world's largest AIDS vaccine trial of more than 16,000 volunteers in
Thailand, researchers announced Thursday in Bangkok.
Even though the benefit is modest, "it's the first evidence that we could
have a safe and effective preventive vaccine," Col. Jerome Kim told The
Associated Press. He helped lead the study for the U.S. Army, which
sponsored it with the National Institute of Allergy and Infectious Diseases.
The institute's director, Dr. Anthony Fauci, warned that this is "not the
end of the road," but said he was surprised and very pleased by the outcome.
"It gives me cautious optimism about the possibility of improving this
result" and developing a more effective AIDS vaccine, Fauci said. "This is
something that we can do."
The Thailand Ministry of Public Health conducted the study, which used
strains of HIV common in Thailand. Whether such a vaccine would work against
other strains in the U.S., Africa or elsewhere in the world is unknown,
scientists stressed.
Even a marginally helpful vaccine could have a big impact. Every day, 7,500
people worldwide are newly infected with HIV; 2 million died of AIDS in
2007, UNAIDS estimates.
"Today marks a historic milestone," said Mitchell Warren, executive director
of the AIDS Vaccine Advocacy Coalition, an international group that has
worked toward developing a vaccine. Warren was not involved in the study.
"It will take time and resources to fully analyze and understand the data,
but there is little doubt that this finding will energize and redirect the
AIDS vaccine field," he said in a statement.
The study tested the two-vaccine combination in a "prime-boost" approach, in
which the first one primes the immune system to attack HIV and the second
one strengthens the response.
They are ALVAC, from Sanofi Pasteur, the vaccine division of French
drugmaker Sanofi-Aventis; and AIDSVAX, originally developed by VaxGen Inc.
and now held by Global Solutions for Infectious Diseases, a nonprofit
founded by some former VaxGen employees.
ALVAC uses canarypox, a bird virus altered so it can't cause human disease,
to ferry synthetic versions of three HIV genes into the body. AIDSVAX
contains a genetically engineered version of a protein on HIV's surface. The
vaccines are not made from whole virus -- dead or alive -- and cannot cause
HIV.
Neither vaccine in the study prevented HIV infection when tested
individually in earlier trials, and dozens of scientists had called the new
one futile when it began in 2003.
"I really didn't have high hopes at all that we would see a positive
result," Fauci confessed.
The results proved the skeptics wrong.
"The combination is stronger than each of the individual members," said the
Army's Kim, a physician who manages the Army's HIV vaccine program.
The study tested the combo in HIV-negative Thai men and women aged 18 to 30
at average risk of becoming infected. Half received four "priming" doses of
ALVAC and two "boost" doses of AIDSVAX over six months. The others received
dummy shots. No one knew who got what until the study ended.
Thanad Yomha, a 33-year-old electrician from southeastern Thailand, said he
didn't expect anything in return for volunteering for the project.
"I did this for others," Thanad said. "It's for the next generation."
Participants volunteered for the study and were told about the potential
risks associated with receiving the experimental vaccine before agreeing to
participate.
All were given condoms, counseling and treatment for any sexually
transmitted infections, and were tested every six months for HIV. Any who
became infected were given free treatment with antiviral medicines. All
participants continued to receive an HIV test every six months for three
years after vaccinations ended.
The results: New infections occurred in 51 of the 8,197 given vaccine and in
74 of the 8,198 who received dummy shots. That worked out to a 31 percent
lower risk of infection for the vaccine group. Two of the infected
participants who received the placebo died.
The vaccine had no effect on levels of HIV in the blood for those who did
become infected. That had been another goal of the study -- seeing whether
the vaccine could limit damage to the immune system and help keep infected
people from developing full-blown AIDS.
That result is "one of the most important and intriguing findings of this
trial," Fauci said. It suggests that the signs scientists have been using to
gauge whether a vaccine was actually giving protection may not be valid.
"It is conceivable that we haven't even identified yet" what really shows
immunity, which is both "important and humbling" after decades of vaccine
research, Fauci said.
Details of the $105 million study will be given at a vaccine conference in
Paris in October.
This is the third big vaccine trial since 1983, when HIV was identified as
the cause of AIDS. In 2007, Merck & Co. stopped a study of its experimental
vaccine after seeing it did not prevent HIV infection. Later analysis
suggested the vaccine might even raise the risk of infection in certain men.
The vaccine itself did not cause infection.
In 2003, AIDSVAX flunked two large trials -- the first late-stage tests of
any AIDS vaccine at the time.
It is unclear whether vaccine makers will seek to license the two-vaccine
combo in Thailand. Before the trial began, the U.S. Food and Drug
Administration said other studies would be needed before the vaccine could
be considered for U.S. licensing.
"This is a world first which proves that vaccine development is possible,"
Supachai said. "But this is not to the level where we can license or
manufacture the vaccine yet."
Mass-producing the vaccine, plus how to proceed with future studies, will be
discussed among the governments, study sponsors and companies involved in
the trial, Kim said. Scientists want to know how long protection will last,
whether booster shots will be needed, and whether the vaccine helps prevent
infection in gay men and injection drug users, since it was tested mostly in
heterosexuals in the Thai trial.
The study was done in Thailand because U.S. Army scientists did pivotal
research in that country when the AIDS epidemic emerged there, isolating
virus strains and providing genetic information on them to vaccine makers.
The Thai government also strongly supported the idea of doing the study.
Associated Press Medical Writer Marilynn Marchione reported from Minneapolis
Study information: http://www.hivresearch.org/phase3/factsheet.html
Vaccine coalition: http://www.avac.org/
UNAIDS: http://tinyurl.com/krq7kr
Government AIDS info: http://www3.niaid.nih.gov/topics/HIVAIDS/
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BWIZA MUHIRE HIPPOLYTE
Central Africa Regional Focal Point
Global Youth Coalition on HIV/AIDS
P.O 30 Huye- Butare/Rwanda
Cell Phone: +250 788 60 42 94
hippolyte (at) youthaidscoalition.org
www.youthaidscoalition.org
www.iAIDS.org
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