The U.S. National Institutes of Health (NIH) this week canceled plans for a large clinical trial of an experimental vaccine to combat the human immunodeficiency virus (HIV). Anthony S. Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases, said that   more research was needed on the government-developed vaccine known as PAVE (Partnership for AIDS Vaccine Evaluation) before it could be tested in 8,500 people infected with HIV, the virus that causes full-blown AIDS. The announcement comes 10 months after drug giant Merck & Co. canceled a trial of a similar vaccine after it was found ineffective at reducing the HIV load in volunteers' blood. Fauci said the trial of the newer vaccine was canceled because there was no indication that it would be any more promising than the earlier version; both used a relatively innocuous cold virus to deliver the drug.