AIDSVAX, a bivalent vaccine consisting of a preparation of recombinant gp120 from two types of HIV, is being developed by VaxGen for the potential prevention of HIV infection. Two versions of the vaccine are in phase III trials: AIDSVAX B/E, in trials in Thailand, stimulates production of antibody to HIV subtypes common to South Asia, South East Asia and countries of the Pacific Rim; and AIDSVAX B/B, in trials in the US and Europe, stimulates the production of antibody to HIV subtypes that are found in the Americas, Europe, the Caribbean and Australia.