Data from a second Phase III clinical trial of VaxGen's experimental HIV vaccine AIDSVAX conducted in Thailand shows that the vaccine has "no noticeable effect on infection rates," the San Francisco Chronicle reports. The trial involved nearly 2,500 Thai injection-drug users, half of whom were given placebo injections during the three-year study. Trial data showed that during the vaccine study, 105 placebo recipients became infected with HIV, while 106 who received the experimental vaccine were infected.
The results were similar to those released in February for a separate Phase III trial of the vaccine among gay and bisexual men and high-risk women in North America. That study showed that AIDSVAX reduced the rate of new HIV infections by just 3.8% among the study participants. VaxGen officials had initially indicated that subset data showed AIDSVAX to be more effective among African-Americans and Asians, but a more in-depth analysis failed to back up those claims.
The two Phase III AIDSVAX clinical trials were the first end-stage studies ever conducted of an experimental HIV vaccine. AIDSVAX is still being studied as part of a dual-vaccine test launched in July in Thailand. AIDSVAX is being used along with Aventis Pasteur's ALVAC in 16,000 HIV-negative volunteers to see if AIDSVAX will boost the effectiveness of ALVAC in preventing new HIV infections. The study is scheduled to last five years.