A new data on an experimental AIDS vaccine that failed to work has shown that volunteers who received shots were more likely to get infected through sex or other risky behaviour than those given dummy shots.
The new details, released on Wednesday by drug maker Merck & Co., however could not answer the question of whether failure of the vaccine also spells doom for many similar AIDS vaccines now being tested.
The report of the data published by the Associate Press noted that the researchers were not sure why more of the vaccinated volunteers wound up getting HIV than those who got dummy shots.
Dr. Keith Gottesdiener, vice president of clinical research at Merck Research Laboratories was quoted as saying, "One of the possibilities is that the increase in the number of infections was related to the vaccine," meaning it could have made people more susceptible to HIV infection.
He could not say how likely that was but said other factors, even coincidence, could be the explanation.
Merck, based in Whitehouse Station, New Jersey, had announced on September 21 that it was stopping the study because the vaccine did not work.
The announcement was viewed by AIDS activist as a stunning setback in the push to develop an AIDS vaccine.
The vaccine is made from a common cold virus with three synthetic HIV genes tucked inside.
It is designed to stimulate the immune system to kill any HIV-infected cells encountered in the future.
But the researchers found that volunteers with pre-existing immunity to this particular cold virus were much more likely to get infected with HIV if they got the AIDS vaccine than if they got the dummy shot.
Some 3,000 people, mostly gay men and female sex workers, had volunteered to get the experimental vaccine or dummy shots.
All were reportedly warned to protect themselves from AIDS exposure.
But by the time the study was halted in September, Merck said 24 of 741 volunteers who got the vaccine in one segment of testing later developed HIV; 21 of 762 participants who got dummy shots also were infected.
The new data showed that to date, 49 of 914 vaccinated men became infected with HIV, compared with 33 of the 922 men who got dummy shots while only one woman and a small number of heterosexual men became infected.
Some optimists did not see the said vaccine failure as anything worth a bother.
According to Dr. Anthony Fauci, head of National Institute of Allergy and Infectious Diseases, "In my mind, this doesn’t damn anything.
"It tells you you need to be very careful with every aspect of vaccine design and testing."
The international testing was partly funded by the American National Institute of Health. Merck’s head of medical affairs for vaccines, Mark Feinberg, said it could be a few years before further data mining and results of other drugmakers’ vaccine tests clear up the mystery.
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