AIDS vaccine made by Crucell has shown success in blocking the AIDS virus in monkeys. The claim has been made by a Harvard scientist.

The scientist wrote in an online journal Nature about the new vaccine. The vaccine was successful in keeping away the virus for up to 500 days. This, he considers, is a breakthrough in developing an AIDS vaccine.

But last year too, New York-based Merck & Co. had developed a similar vaccine, which benefitted monkeys, failed in human testing. The problem with the vaccine seemed to be linked with a cold virus in the vaccine, which unexpectedly raised people's risk of getting infected with AIDS.

Dan Barouch, the lead author and a virologist at Harvard University and Beth Israel says that Crucell-Harvard vaccine won't be used in humans because it contains the same cold virus. Its effects will be under investigation on monkeys for some more time before it is finally tested on humans.

``It certainly is better than the previous animal models, but we still don't know -- and it's a big if - whether this is going to translate into a meaningful and useful human model,'' Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said in a Nov. 7 telephone interview.