The long awaited results of the first phase III HIV vaccine study released today show that Vaxgen’s AIDSVax offered no significant protection against HIV infection in the study population as a whole. However the study did show a statistically significant reduction in HIV infections among black and Asian volunteers, which correlated with a higher level of vaccine-induced neutralising antibodies.
AIDSVax was tested in 5,417 volunteers in North America and the Netherlands in a 36 month randomised placebo controlled study. 5,009 volunteers received at least three of the seven scheduled vaccinations.
|Number of volunteers to complete three immunizations:||5,009|
|Non-white volunteers (Black, Asian, Other):||498|
|Annual study infection rate||2.7%|
Approximate Efficacy (after at least 3 primary doses)
|All volunteers:||3.8% (p-value = 0.76; confidence interval: -23% to 24%)|
|Non-white volunteers:||67% (p-value < 0.01; confidence interval: 30% to 84%)|
|Black volunteers:||78% (p-value < 0.02; confidence interval: 29% to 93%)|
The results appear to suggest that AIDSVax may be more effective in individuals of African origin. All participants were infected with HIV-1 subtype B, so this result does not imply that AIDSVax is more effective against subtypes of HIV found in Africa, Asia and Latin America.
However, Seth Berkley, President of the International AIDS Vaccine Initiative, highlighted the limitations of this finding.
"The results on AIDSVAX must be further analyzed, and independently reviewed. For example, VaxGen's preliminary analysis of the small number of nonwhite volunteers suggests that there were fewer infections among black volunteers who received AIDSVAX than blacks who received the placebo. However, it is difficult to draw conclusions about what this means, given that the number of blacks in the study was so small (VaxGen's analysis is based on just 13 infections among black volunteers, 4 in the vaccine group and 9 in the placebo group).”
Vaxgen says that although the subgroup sample sizes were relatively small compared to the entire study sample, the results are statistically significant.
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”, the company said in its press release. “There is less than a 2% possibility that the observed difference in infection rates among black volunteers could have occurred by chance. In addition to the results in those receiving three doses, the reduction in infection in individuals who received at least one dose of vaccine or placebo were similar and also statistically significant.”