Questions Linger in VaxGen Trial - TheStreet

Updated from 7:56 a.m. EST

Despite a failure that dealt a body blow to stockholders and a huge disappointment to AIDS medicine,



says it will keep studying its experimental HIV vaccine to find out why some racial groups appeared to develop more AIDS resistance than others in a clinical trial.

After being halted since late Friday, the shares recently opened down $7.24, or 56%, to $5.78.

VaxGen's 5,400-person trial of its vaccine, AIDSVAX, showed no statistically significant reduction in HIV infection among its high-risk populace, the company disclosed earlier, although among blacks and Asians the results were more encouraging.

AIDSVAX cut incidence of HIV infection over the entire group by just 3.8%, but among minorities other than Hispanics, there were 67% fewer infections among recipients who got the drug instead of a placebo. Among blacks who got the vaccine, there were 78% fewer HIV infections.

"Although the subgroup sample sizes were relatively small compared to the entire study sample, the results are statistically significant," VaxGen said. "With regard to ethnic minorities in the trial, there is less than a 1% possibility that the observed difference in infection rates could have occurred by chance. There is less than a 2% possibility that the observed difference in infection rates among black volunteers could have occurred by chance."

Comparing the relative rate of infection among these groups returns a slightly less impressive-seeming difference: according to data supplied to the

New York Times

, the rate of HIV infection among African-Americans, Asian and other minorities was 3.7%, compared with 9.9% in the placebo group.

Still, according to VaxGen: "This is the first time we have specific numbers to suggest that a vaccine has prevented HIV infection in humans," adding that the black and Asian volunteers appeared to produce higher levels of antibodies against HIV.

"We're not sure yet why certain groups have a better immune response, but these preliminary results indicate that a surface-protein vaccine that stimulates neutralizing antibodies correlates with prevention of infection."