STEP study of Merck's HIV vaccine to be unblinded

Merck & Co., Inc. and the HIV Vaccine Trials Network (HVTN) have announced that study volunteers in the STEP study of Merck's HIV vaccine (V520) will be told whether they received vaccine or placebo, and all study volunteers will be encouraged to continue to return to their study sites on a regular basis for ongoing risk reduction counseling and study-related tests.

Study investigators are being advised this week to provide this information to the volunteers; volunteers will receive additional information about the unblinding process directly from study sites.

The study was co-sponsored by Merck & Co., Inc.; the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health; and the HIV Vaccine Trials Network (HVTN), which is funded by NIAID. The STEP Study Oversight Committee, which is comprised of representatives from the three study co-sponsors, made the decision to unblind study volunteers following extensive discussion of the STEP results at last week's meeting of the HVTN by researchers, members of the community advisory boards of the study sites and other study site staff, including clinic coordinators and community educators.

On Sept. 21, 2007, the trial sponsors announced that vaccinations in the study were discontinued because the vaccine was not effective, and the available results from the study were presented at last week's meeting of the HVTN.