When the National Institutes of Health (NIH) canned its HIV vaccine trial in April, the field, yet again, lost its brightest hope. Since then, NIH has continued to monitor participants in the trial, and this week it presented an update in the New England Journal of Medicine.
The good news is the follow-up data quash fears that the vaccine increases the risk of contracting HIV. When the trial was stopped, there were more HIV infections in the vaccine group than the placebo arm, raising concerns that the vaccine did more harm than good. The difference between the groups--which fell short of a statistically significant result in April--has narrowed over the past 5 months. With memories of the rise in HIV among men who received Merck's ($MRK) vaccine in the 2007 STEP trial still fresh, the new NIH data was a relief.
"My biggest concern was that it was going to be harmful. The study should never have gone forward. The scientific rationale to do it, after STEP, was in my mind not there," Dr. Carlos del Rio, an investigator on the STEP trial, told MedPageToday. Both vaccines use a recombinant adenovirus-5 (Ad5) vector, a delivery vehicle that was linked to the increased risk of HIV infection in the Merck trial. However, the NIH trial researchers point out that deletions in the adenovirus genome and HIV-1 gene inserts make the Ad5 in their vaccine different than the vector used in STEP.
Researchers will continue to monitor participants in the NIH trial, but it appears confirmation the vaccine doesn't increase risk of infection is the most optimistic outcome. "The study definitively showed that the DNA/rAd5 vaccine regimen did not reduce either HIV-1 acquisition or the viral-load set point, as compared with placebo," the researchers wrote in NEJM.