HIV Thai Phase III Update

Experimental HIV Vaccine Prevents Infection in Nearly 1/3 of Subjects

Researchers optimistic, but questions remain

On Thursday, September 24, 2009, The Surgeon General of the U.S. Army released results from the Thai Phase III HIV vaccine study that demonstrated modest results in preventing HIV infection among participants in the clinical trial. The study found the vaccine regimen to be safe and 31 percent effective in preventing HIV infection.

The potential breakthrough comes after several failed vaccine trials; many scientists believed an HIV vaccine might not be possible. For the first time, however, the Thai Phase III study used the combination of two vaccines, Sanofi Pasteur’s ALVAC vaccine and the AIDSVAX B/E vaccine, developed by Vaxgen Inc. and licensed to the nonprofit Global Solutions for Infectious Diseases (GSID) in 2008. The research was sponsored jointly by the U.S. Army and the National Institute of Allergy and Infectious Diseases (NIAID), along with Sanofi Pasteur and GSID.

The study, conducted in two Thai provinces, began in October 2003 and involved approximately 16,402 HIV-negative subjects ages 18-30 at various levels of risk for HIV infection. Trial participants were evenly divided into groups and received either the vaccine or placebo upon enrollment in the study and again after 1 month, 3 months, and 6 months. Participants were counseled on HIV risk reduction strategies and tested for the virus twice a year for three years. Among the 8,197 subjects who received the combination of vaccines, 51 contracted HIV during the study. This compares to 74 of the 8,198 participants in the placebo group who became infected with the virus. Those who became HIV-positive during the study have been offered treatment at no cost.

In a press release, Anthony S Fauci, M.D. and Director of the National Institute of Allergy and Infectious Diseases, acknowledges these new findings as “an important step forward in HIV vaccine research,” but cautions that “additional research is needed to better understand how this vaccine regimen reduced the risk of HIV infection.”

The United Nations Joint Programme on HIV/AIDS estimates that 7,000 people worldwide are newly infected with HIV everyday; 2 million people died of AIDS in 2007. There is much to consider regarding future HIV vaccine research. Yet, after more than two decades, the search for a safe, effective vaccine that protects against HIV infection has made an encouraging advance.

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