A safe and effective vaccine for the prevention of human immunodeficiency virus type 1 ( HIV-1 ) infection is a global priority.
Researchers have tested the efficacy of a DNA prime-recombinant adenovirus type 5 boost ( DNA/rAd5 ) vaccine regimen in persons at increased risk for HIV-1 infection in the United States.
At 21 sites, researchers have randomly assigned 2504 men or transgender women who have sex with men to receive the DNA/rAd5 vaccine ( 1253 participants ) or placebo ( 1251 participants ).
Investigators have assessed HIV-1 acquisition from week 28 through month 24 ( termed week 28+ infection ), viral-load set point ( mean plasma HIV-1 RNA level 10 to 20 weeks after diagnosis ), and safety.
The 6-plasmid DNA vaccine ( expressing clade B Gag, Pol, and Nef and Env proteins from clades A, B, and C ) was administered at weeks 0, 4, and 8.
The rAd5 vector boost ( expressing clade B Gag-Pol fusion protein and Env glycoproteins from clades A, B, and C ) was administered at week 24.
In April 2013, the Data and Safety Monitoring Board has recommended halting vaccinations for lack of efficacy.
The primary analysis showed that week 28+ infection had been diagnosed in 27 participants in the vaccine group and 21 in the placebo group ( vaccine efficacy, -25.0%; P=0.44 ), with mean viral-load set points of 4.46 and 4.47 HIV-1 RNA log10 copies per milliliter, respectively.
Analysis of all infections during the study period ( 41 in the vaccine group and 31 in the placebo group ) also showed lack of vaccine efficacy ( P=0.28 ).
The vaccine regimen had an acceptable side-effect profile.
In conclusion, the DNA/rAd5 vaccine regimen did not reduce either the rate of HIV-1 acquisition or the viral-load set point in the population studied. ( Xagena )
Hammer SM et al, N Engl J Med 2013; 369:2083-2092