In 1998, the first vaccine for the prevention of HIV/AIDS (Aidsvax) entered Phase III trial, the first large-scale human trial of an HIV vaccine. The trial involved more than 5,400 volunteers from the U.S., Canada, and the Netherlands, the majority of whom were men who have sex with men. Preliminary results from the trial AIDS VAX (VaxGen) vaccine were reported in early 2003. The HIV vaccine appeared to show a protective effect among non-Caucasian populations, especially African Americans, although sample sizes were small. However, for the majority of the participants, who were Caucasians, the effect of the vaccine was minimal.