Merck HIV Vaccine Fails in Clinical Trial

Merck’s investigational HIV vaccine V520 failed to prevent infection in previously uninfected subjects and may have increased the risk of infection in some participants.

Volunteers with preexisting immunity to the cold virus used as a carrier for the synthetic HIV genes in the vaccine suffered from an increased number of HIV infections, the company said in reporting the results of the STEP study, one of two Phase II trials. Moreover, the vaccine did not reduce viral loads in volunteers who became infected with HIV during the trial. However, Merck said, the vaccine itself cannot cause HIV infection.

The most recent vaccine clinical trial analyses are available at www.hvtn.org. Additional analyses are under way and will be released as more information becomes available. A presentation is scheduled at the Conference on Retroviruses and Opportunistic Infections in Boston in February 2008.