South African Press Association - February 13, 2007

"A vaccine is at least a decade away ... in the event of the Merck vaccine hitting the bar, it will happen earlier," said Dr Wayne Koff, senior vice-president of the IAVI.

Koff spoke of the latest challenges and the future direction of HIV-vaccine development at the Wanderers Club in Johannesburg on Tuesday.

The Merck vaccine was developed by American company Merck. It is called MRKAd5 and hailed as an "historic milestone in the fight against Aids".

The vaccine will soon enter its final stages of study -- trials involving about 3 500 HIV-negative male and female volunteers -- which will last four years.

MRKAd5 uses the vector Ad5, an element of the vaccine modified by a harmless virus meant to stimulate cellular immune response in the body. Ad5 causes a common cold.

"There is a theoretical possibility that a vaccine based on Ad5 could potentially have problems ... It could be effective, but not effective in individuals who have high amounts of Ad5 antibodies," Koff said.

The IAVI and other organisations are developing second-generations vectors, Ad35 and Ad11, should this problem (high numbers of Ad5 antibodies) arise. "It is prudent to plan for success, for moderate success as well as for failure."

Scientists know more about HIV than any other virus on the planet, yet 10 people are infected with the disease every minute, said Koff.

He said a problem experienced by the scientific community is one of capacity rather than the already gargantuan challenge of finding a vaccine.

"The reality of the Aids vaccination effort is we have the best and the brightest minds working on it about 10% of the time. The rest of their time is spent on writing grant applications," he said. "We need to figure out a way to harness that talent and get them working 100% of the time, perhaps through new management structures."

Another difficulty scientists are facing is the difference in strains of the virus across the world.

An ideal vaccination would be to block it early, when it enters the body. However, this is a major challenge. A second goal, for which most scientists are aiming, is to control and slow down the progress of the disease, said Koff.

He said the best vaccines are those where weaker forms of the virus are used -- called live attenuated vaccines -- but this proves difficult with the HI virus.

"This virus is very smart; every time you try to weaken it in the lab, it changes right back to the wild virus it was ... no one is working on this at present," he said.

Despite the challenges, Koff believes vaccination is the key to eliminating HIV, but stressed that it will be a long journey. "It's a long, long journey, but we are going to get there. It is a marathon not a sprint," he said.

The IAVI is a global non-profit organisation working to speed up the search for a vaccine to prevent HIV infection and Aids.

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