The search for an HIV vaccine took yet another hit as a major trial was halted early because the vaccine under investigation showed no protective effect, MedPage Today reports. Publishing their findings in The New England Journal of Medicine and also presenting them at the AIDS Vaccine 2013 conference in Barcelona, investigators had enrolled in their trial a total of 2,504 men who have sex with men (MSM) and transgender women who have sex with men.

After a series of injections, the participants were followed for 24 months. At the point when the safety committee put a stop to the trial, 1,914 participants qualified for analysis. Twenty-seven members of the vaccine group and 21 in the placebo group acquired HIV. The difference was not statistically significant, meaning it could have occurred by chance.

The vaccine used a collection of segments of DNA derived from HIV in order to prime the immune system.  Next an adenovirus vector expressing HIV proteins was given as an immune booster.

Despite the fact that the vaccine prompted both cellular and humoral immune response, it failed to lower what's known as the viral set-point, which is the level at which the viral load eventually reaches a homeostasis—or equilibrium—without antiretroviral intervention. The average viral load for both groups was around 30,000.

Appeasing a major concern of the researchers, the vaccine did prove safe.

To read the MedPage Today story, click here.
 
To read the study, click here.