Vaccine "failure" exposes Aussies to AIDS virus

ABC News
Nov. 09, 2007

Nine Australians are believed to be among thousands of people who are unaware a once-promising vaccine for AIDS has increased their infection risk, after they participated in clinical trials around the world.

The multinational trials involving more than 3,000 HIV-negative volunteers were cancelled in September after a large-scale study found the vaccine was not effective at preventing infection.

Researchers have this morning revealed far worse news - those who received the V520 vaccine are more susceptible to acquiring the AIDS virus.

It is understood nine of the 18 people from Sydney involved in the study were given the HIV vaccine but do not know.

The volunteers were warned to protect themselves from exposure to AIDS but were not told if they were administered the vaccine or the inactive placebo.

The information was kept secret to minimise biases in the study.

Scientists will decide over the next 10 days whether those involved in the trial should be told about whether they were given the vaccine or not.

US pharmaceutical giant Merck, which helped develop V520, says volunteers can opt out of the study now and be told if they were given the HIV vaccine.

All but one of the infections were in male volunteers and the bulk of those infected were homosexual men.

Scientists baffled

The study started 18 months ago after 20 years of research and development to get the vaccine to human trials.

Its chief researcher in Australia, Dr Tony Kelleher from the University of New South Wales, told ABC reporter Karen Barlow in May last year there was no chance for the vaccine to cause HIV infection because it carried so little of the virus.

Researchers say that is still the case but somehow things went horribly wrong with the phase-two trial.

Of the people who had the HIV vaccine, 49 became infected with the virus, whereas only 33 in the placebo group became infected.

The vice-president of Merck's research team, Keith Gottesdiener, says the trial was abruptly stopped two months ago because V520 was not preventing infection.

"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," he said.

"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."

Doctor Larry Corey from the US Vaccine and Infectious Disease Institute says its too soon to establish whether the virus caused the increased infection rates.

"One of the possibilities is that the increase in the number of infections could be related to the vaccine, there are many other possibilities as well," he said.

"My own opinion is that it's way too early to really answer and the data is way too complex and there's no simple answer to that question."

Cold virus

The trial vaccine used a disabled form of the common-cold virus to carry three synthetically produced HIV genes into the body.

It appears people who had higher levels of immune protection against the virus before getting the vaccine were at highest risk of acquiring HIV.

The vaccine did not contain live HIV. It had been well tolerated in smaller clinical trials and had produced immune responses.

The trial was also conducted in North America, South America, the Caribbean and South Africa.