A Pivotal Step for HIV Vaccines

Investigators continue to explore why the HIV vaccine used in the Step Study failed to protect high-risk individuals from HIV acquisition — and seemed to increase risk in some.

The development of an effective HIV vaccine was thrown a complex and disheartening curve in late 2007 when investigators halted a large phase IIB clinical trial of a vaccine designed to elicit cell-mediated immune responses to HIV (AIDS Clin Care Oct 1 2007). The much-discussed results of this trial (called the Step Study) now have been published with expanded analyses, including immunologic findings.

The trial involved 3000 men and women at high risk for HIV acquisition who were randomized to receive either placebo or a vaccine composed of three recombinant adenovirus serotype 5 (Ad5) vectors containing gag, pol, and nef genes derived from clade B HIV-1. Approximately 38% of study participants were women, and more than 96% of the men report…

Reviewing Author

Frances Priddy, MD, MPH

A Pivotal Step for HIV Vaccines

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Reviewing Author