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Aids vaccine 'increased risk'
08/11/2007 17:39 - (SA)
Chicago - A once-promising vaccine for Aids may have inadvertently increased the infection risk of people participating in clinical trials, researchers said on Wednesday.
The multinational trials involving more than 3 000 HIV-negative volunteers were cancelled in September after a large-scale study found it was not effective at preventing infection.
Further analysis showed that those who received the vaccine had a higher rate of infection than those who received a placebo, said US pharmaceutical giant Merck, which helped develop the vaccine.
The study volunteers who received the vaccine are being advised of their potentially increased susceptibility, Merck said.
"We are analysing the data to try to determine if the results are due to immune responses induced by the vaccine, differences in study populations, or some other biological phenomenon we don't yet understand, or simply due to chance," said Keith Gottesdiener, vice president of Merck's vaccine and infectious disease clinical research.
"It will take some time before we understand why the vaccine did not work and why there was a trend toward more cases of infection in volunteers who received the vaccine," he said in a statement.
The experimental vaccine cannot cause infection, Merck said.
It was a modified cold virus used to deliver three synthetically produced HIV genes in the hopes of stimulating a response from the immune system.
The randomised, double-blind trials were conducted in various sites in North America, South America, the Caribbean, Australia and South Africa.
All but one of the infections were in male volunteers and the bulk of those infected were homosexual men.
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HIV/Aids Special Report
