"No significant efficacy information is yet available on any candidate AIDS vaccine, though over 30 candidate HIV vaccines have been evaluated in over 60 clinical trials worldwide since 1987," said Margaret Johnston from the US National Institute of Health.

However, the scientists hold that safe and effective AIDS vaccines would still be among the best medical and cost effective prevention tools.

They called for further fundamental studies, lab experiments, and clinical evaluations, along with considering social and ethical issues.

In a major development in this effort, Chinese scientists and their foreign counterparts agreed tonight to jointly set up a laboratory.

The NCAIDS signed an agreement with the Aaron Diamond AIDS Research Center of the US to start a clinical virology lab in Beijing, through which information, technology and research personnel will be exchanged between China and the US

David Ho, internationally-known researcher of the well-known " cocktail" combination therapy against HIV and the head of Aaron Diamond center under the Rockefeller University, said that he has long hoped to work with the Chinese counterparts to tackle the increasing problem of HIV/AIDS in China.

China is feared to have more than 400,000 HIV carriers since the first AIDS case was reported in 1985. (Xinhua)