There are a number of studies being performed to test HIV vaccines. The vaccines that seem to be the most promising are canarypox vaccines, known as ALVAC vaccines. The three experimental HIV vaccines used in this study are called ALVAC-HIV vCP205, HIV-1 SF-2 p24, and HIV-1 SF-2 rgp120. The HIV-1 SF-2 p24 and HIV-1 SF-2 rgp120 vaccines are mixed with an adjuvant, which is a substance that increases immune response.