First Try at AIDS Vaccine Flops
Possible Effect Claimed for Blacks, Asians
Feb. 24, 2003 -- AIDSVAX doesn't work. That's the main finding from the first large-scale test of an AIDS vaccine. Yet a glimmer of hope remains for this controversial product.
That hope comes from the very small number of blacks and Asians enrolled in the trial. Of the more than 5,000 people who took part in the study, only 500 were "black, Asian, or other." Overall, the vaccine had no effect. But if one looks only at these ethnic minorities, the vaccine appeared to work.
In a news conference to announce the results, VaxGen -- the company that makes AIDSVAX -- stressed the minority findings.
"When all volunteers are analyzed, the vaccine did not appear to be effective," said VaxGen president Donald P. Francis, MD. "When all volunteers are broken down by race and ethnicity, white and Hispanics again show no evidence of vaccine efficacy. On the other hand black, Asian, and other subgroups showed clear evidence of vaccine efficacy -- 66.8%. And if just the black volunteer group is considered, we see a vaccine efficacy of 78.3%. Both of these are highly significant. The chance of these occurring by coincidence would be less than 1 in 100."
It's hard to know how much to trust this finding. The 78% efficacy claim for blacks, for example, is based on only 11 HIV infections -- four among the 203 blacks who got the AIDS vaccine, and nine among the 111 blacks who got fake injections. This seems very odd compared with the 3.8% efficacy seen in the entire study.
Why would a vaccine work for some races and not for others? Michael Para, MD, of Ohio State College of Medicine, put forward a theory at the VaxGen news conference. Para is one of several independent researchers to review the study findings.
"You might think, 'Why in the world should this vaccine work for blacks and not for whites?'" Para says. "We know there are genetic differences between blacks and whites, specifically in the way we respond to different infections. I take care of a lot of HIV patients, and there is increasing data that certain genetic types respond poorly to HIV infection, and there are certain genetic types that respond better. ... So while the results are surprising, I don't think they are outside of scientific explanation."
Other AIDS vaccine researchers are more skeptical. One is Mark Feinberg, MD, PhD, medical director of the Hope Clinic at Emory University's Vaccine Research Center.
"I am not aware of any racial difference in response to vaccines or to drugs where the magnitude is as substantial as this zero versus 78% efficacy they report," Feinberg tells WebMD. "They have a ways to go to provide an explanation for that. And why wouldn't you see that same genetic predisposition in the white and Hispanic categories as you see in black or other minorities? ... It seems surprising that the only beneficial effects of the vaccine are seen in racial groups where the numbers are the smallest."