The STEP Study Provides a Hint That Vaccine Induction of the Right CD8+ T Cell Responses Can Facilitate Immune Control of HIV

(See the article by Fitzgerald et al., on pages 765–72.) The STEP study was a large, random-ized, placebo-controlled, test-of-concept vaccine trial using an Ad5 vector ex-pressing human immunodeficiency virus (HIV)–1 Gag, Pol, and Nef designed to induce T cell immunity to HIV-1. This trial was stopped and unblinded in 2007 after an interim analysis showed that the vaccine did not achieve efficacy for the 2 primary study end points, HIV-1 acquisition and plasma HIV-1 RNA levels 3 months after di-agnosis of HIV-1 infection, and sug-gested that vaccinated individuals with