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JOHANNESBURG,
Oct. 24 - South African AIDS researchers have begun
warning hundreds of volunteers that a highly touted
experimental vaccine they received in recent months
might make them more, not less, likely to contract HIV
in the midst of one of the world's most rampant epidemics.
The
move stems from the discovery last month that an AIDS
vaccine developed by Merck & Co. might have led
to more infections than it averted among study subjects
in the United States and other countries. Among those
who received at least two doses of the vaccine, 19 contracted
HIV compared with 11 of those given placebos.
Researchers
shut down the trial on the grounds that the vaccine
was proving ineffective, but the surge in infection
among vaccinated volunteers prompted intense scientific
debate and anxiety among researchers. The failure of
the Merck vaccine is the latest in a series of disappointing
results for research projects aimed at curbing AIDS.
"This
is my worst nightmare," said Glenda Gray, the lead
South Africa investigator for the vaccine study. "I
haven't slept for days. I have a headache. I'm ready
to resign from trials for the rest of my life."
Researchers
in Soweto, Cape Town, Durban and two other sites began
contacting South Africa's 801 trial participants on
Tuesday, mainly by cellphone text message. The goal
is to tell each one individually whether they had received
a placebo or the vaccine, a process called "unblinding"
the trial. Researchers are telling the roughly half
who received the vaccine that it might have increased
their risk of contracting HIV.
"It's
quite shocking," said Nelly Nonoise, 26, who had
received three injections of the vaccine in her left
shoulder.
She
added, "I probably wouldn't have joined the study
knowing there's a risk. "
Another
participant, Nonhlanhla Nqakala, 22, said she thought
the text message urging her to visit the vaccine test
site meant she had tested positive for HIV. Her brother
and a close friend had the disease and died, she said.
Nqakala
said she was relieved when a doctor explained that she
was not infected, but the news of a possible problem
with the vaccine -- she had received three doses, not
placebos -- left her distressed. "I thought the
trial would help us find a cure for HIV," she said.
Merck
developed the vaccine in conjunction with the U.S. National
Institutes of Health, and until September's announcement,
researchers worldwide considered it the most promising
candidate yet in a multibillion-dollar quest for an
AIDS vaccine dating to the 1980s.
Scientists
crafted the vaccine by genetically altering a common
virus to include elements of HIV. They hoped that it
would trigger an immune response that would make recipients
less likely to contract HIV, or at least delay the onset
of full-blown AIDS.
The
vaccine could not have caused infection, researchers
say, but it could have caused immunological changes
that made it easier for the virus to take hold during
a later exposure.
The
Merck vaccine trials took place in 15 cities in the
United States, including Boston, Los Angeles and New
York, and three in Canada. There also were sites in
Peru, Brazil, Australia, Haiti, the Dominican Republic
and Jamaica. Those trials began in December 2004 and
included 3,000 participants, mostly gay men.
In
South Africa -- where an estimated 5.5 million people
are infected with HIV, more than in any other country
-- the study used the same vaccine but was administered
separately. The trial here started later, with the first
injections this year, and had its own ethics oversight
board. Most of the subjects were heterosexual.
The
ethics oversight board in the United States, which monitored
the trial everywhere but in South Africa, has not decided
whether to tell participants if they received the placebo
or the vaccine, said Mark Feinberg, vice president for
medical affairs and policy for Merck.
Continuing
research could be compromised, he said, if participants
were told immediately whether they received the placebo
or the vaccine. Vaccine researchers are scheduled to
meet in Seattle on Nov. 7.
"Given
the complexity of the issue, we feel the best conclusions
will be reached when all the data are analyzed in their
entirety," Feinberg said from Atlanta, where he
was traveling.
He
added that individual participants who want to know
whether they received the vaccine will be told. Researchers
also are counseling all study participants that the
vaccine may have increased HIV risk for those who received
it.
Other
AIDS studies also have had unexpected results. Trials
of two vaginal microbicide gels to prevent HIV led to
more infections among those using the products instead
of placebos. A massive study in Zimbabwe of the ability
of HIV counseling and testing to prevent the spread
of the epidemic found more infections among those with
expanded access to testing.
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