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Disappointing Results from Another HIV Vaccine Efficacy Trial

October 8, 2013

Disappointing Results from Another HIV Vaccine Efficacy Trial

  1. Carlos del Rio, MD

The HVTN 505 study, which tested a DNA prime–recombinant adenovirus type 5 vector boost vaccine regimen in people at increased risk in the U.S., failed to provide any protective effect.

  1. Carlos del Rio, MD

Only one of five previous HIV vaccine efficacy trials has demonstrated even a modest reduction in infection risk (NEJM JW AIDS Clin Care Oct 22 2009). Now, the HIV Vaccine Trials Network has reported the results of a randomized, double-blind, placebo-controlled, phase IIb efficacy trial of a multigene, multiclade DNA prime–recombinant adenovirus type 5 vector boost vaccine in at-risk populations in the U.S.

A total of 2499 HIV-uninfected individuals (98% men; 70% white; median age, 29) were included in the analysis. All had substantial sexual risk behaviors for HIV infection, such as unprotected insertive or receptive anal intercourse.

HIV infection was diagnosed in 72 individuals during follow-up. Forty-eight of these infections occurred after week 28 (at which time the 4-dose series would have been completed) and were included in the primary endpoint analysis. Of these 48 infections, 27 occurred in the vaccine group and 21 in the placebo group (annual incidences, 2.8% and 2.3%, respectively). Among individuals who became infected, the HIV viral-load set points were similar between arms (mean, 4.46 and 4.47 log copies/mL). The vaccine was found to be safe, with no increased risk for HIV infection among vaccinees, as was seen in the Step Study (NEJM JW AIDS Clin Care Dec 8 2008). Having more than three male sex partners or having unprotected receptive anal intercourse during the 3 months before enrollment was highly predictive of risk for HIV infection among study participants.

Comment

The study vaccine failed to prevent HIV infection or to decrease the viral-load set point among those who became infected. This trial again demonstrates that developing an effective HIV vaccine is much harder than initially thought. Many of us remember when Margaret Heckler, then Health and Human Services Secretary, announced in 1984 that we would have an effective HIV vaccine within 10 years. How wrong she was, and what a humbling experience for science the development of a vaccine has been!

  • Disclosures for Carlos del Rio, MD at time of publication Consultant / Advisory board Gilead Sciences; Pfizer Grant / research support CDC; NIH Editorial boards AIDS Research and Human Retroviruses; Journal of AIDS Leadership positions in professional societies HIV Medicine Association (Board of Directors); Infectious Diseases Society of America (Board of Directors); International AIDS Society-USA (Board of Directors)

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