Higher HIV/AIDS risk after getting AIDS vaccine?
Pastor Dale Morgan
Higher HIV/AIDS risk after getting AIDS vaccine?*
'The data are disappointing and puzzling, but we don't have definitive
answers'
HIV experts wrestle with troubling vaccine study at Seattle meeting
Sabin Russell, Chronicle Medical Writer
Thursday, November 8, 2007
San Francisco Chronicle
Evidence is building that an experimental AIDS vaccine given to 1,500
volunteers not only failed to protect those who received it, but may
have put some of them at higher risk of contracting HIV than those who
were given a placebo.
At a Seattle meeting held Wednesday to discuss the latest findings,
vaccine experts wrestled with the complex questions raised by the
disappointing early results of the study, first disclosed by drugmaker
Merck & Co. nearly seven weeks ago.
Enrollment in the study was halted at the time, but researchers are
still tracking the HIV status of the participants.
"The data are disappointing and puzzling, but we don't have definitive
answers" why the results turned out as they did, said Dr. Lawrence Corey
of the Fred Hutchinson Cancer Research Center and leader of the study.
The Merck vaccine was made from a cold virus that was genetically
engineered to carry three genes from HIV, the virus that causes AIDS.
Scientists say it is absolutely impossible to contract HIV from the
vaccine itself. The cold virus was also weakened so that it would not
make the patient ill.
Additional numbers released Wednesday revealed a total of 49 new HIV
infections among men who were assigned the experimental vaccine; and 33
among those given a placebo. A further breakdown of those numbers found
that the risk of infection was doubled among a group of men who carried
high levels of antibodies to a common cold virus - similar to the
hobbled cold virus used as a component of the vaccine.
In that group, 21 new infections were discovered among those getting the
real vaccine, nine among those given a placebo.
Everett Holden, 34, of San Francisco, was one of 137 Bay Area residents
who volunteered to be a human guinea pig. He, like the other volunteers,
has not been told whether he was given three injections of vaccine or
placebo, but he said it was a little frightening to learn that the
experiment might increase his risk. "It's the last thing you would have
expected from participating in the study," he said.
Researchers will decide within 10 days whether to disclose to the 3,000
participants which of them received the vaccine. To do so would give
volunteers some potentially useful information about their risk of
contracting the AIDS virus, but it would also put a quick end to the
experiment before scientists can fully understand the results.
A study of a similar Merck vaccine in South Africa was halted at the
same time as the North and South American trials, but participants there
have been told whether they received the vaccine or placebo. Only 58
volunteers had received all three shots in the test.
Holden said that he is not in any hurry to find out if he might be at
higher risk. "The reason I got into this study was to make a
difference," he said. "If there is still something to be learned, I'm
willing to continue."
But he said the results have spooked some of his friends. "When I signed
up, people were saying, 'Don't do it,' " he said. "Now they are looking
at me and saying, 'I told you so.' I'm afraid this might affect people's
participation in future studies."
The Merck vaccine was designed to train a person's immune system to
attack any blood cells infected by HIV. Although such a vaccine might
not always keep a person HIV-negative, the hope was that it might help
an infected person to control the level of virus in the bloodstream,
just like AIDS drugs do. But the early results showed the vaccine
neither prevented infection, nor kept the level of virus down in those
who were infected anyway.
Dr. Anthony Fauci, director of the National Institute of Allergy and
Infectious Diseases, which co-sponsored the study, said the unexpected
results have pushed back a plan to test a similar vaccine this winter.
"We are certainly interested in mining the data of the Merck trial to
see if we get any clues," he said.
The forthcoming trial, which was to have started in January, would have
enrolled 8,500 volunteers. Now, it won't begin until at least this summer.
Fauci said the finding that people with high levels of antibodies
against the cold virus might be at higher risk of infection after
vaccination poses a troubling dilemma for operators of the study.
"Ethically speaking, you may have to tell someone they have to be more
careful," he said.
There are several plausible explanations for why those who received the
Merck vaccine appeared to have greater susceptibility to HIV infection.
One is simply the result of chance - the number of infections is still
small, and the smaller the number, the more bad luck can play a role.
Another possibility is that those with the strongest immune response to
the cold virus sent armies of white blood cells to attack the vaccine -
but instead of protecting the patients, these activated blood cells
provided a richer target for HIV, which attacks immune cells.
Dr. Seth Berkley, founder and president of the International AIDS
Vaccine Initiative in New York, stressed that disappointing results are
part of the scientific process. "We're anything but finished," he said.
"What I hope doesn't come out of this is hopelessness."