scipaHIV vaccine may increase susceptibility to HIV
November 21st 2007 18:13
Oh, boy.... Merck is under some heavy fire after it developed an HIV vaccine that failed to pass clinical tests. And now comes word that the trial participants may now be even more vulnerable to HIV than before.
The trial was suspended in September when it was realized that the vaccine failed to protect the participants from infection... since then, however, participants that were immune to the weakened viral vector used and had taken the vaccine, were more likely to become HIV-positive.
Chilling news indeed. Unfortunately, the statistics from the trial don't shed light on the mechanism of infection, but the directors of the trial are unable to ignore the significant effect.
One of the cruelest ironies in this experiment: researchers want to test the vaccine on individuals without an immunity to the viral vector, adenovirus-5, but that would mean excluding a large portion of the African sub-Saharan population, the very group they are trying to protect:
The trial was suspended in September when it was realized that the vaccine failed to protect the participants from infection... since then, however, participants that were immune to the weakened viral vector used and had taken the vaccine, were more likely to become HIV-positive.
"Among male volunteers who had high levels of antibodies against the adenovirus, 21 of 392 became infected in the vaccinated group, but only 9 of 386 were infected in the placebo group. The vaccine did not affect infection rates in men with no adenovirus-5 immunity."
Chilling news indeed. Unfortunately, the statistics from the trial don't shed light on the mechanism of infection, but the directors of the trial are unable to ignore the significant effect.
One of the cruelest ironies in this experiment: researchers want to test the vaccine on individuals without an immunity to the viral vector, adenovirus-5, but that would mean excluding a large portion of the African sub-Saharan population, the very group they are trying to protect:
"Researchers are nevertheless concerned. One possible solution is to limit future trials of adenovirus-5-based vaccines to participants with very low levels of immunity to the vector, says Gary Nabel, director of the Vaccine Research Center at the National Institutes of Health in Bethesda, Maryland. But doing so would close off the trials to a large proportion of the population they aim one day to help: more than 80% of sub-Saharan Africans have significant levels of adenovirus-5 immunity. In addition to the planned HIV-vaccine trial, an Ebola vaccine in development also relies on an adenovirus-5 vector."
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