When California-based VaxGen announced in February that its HIV vaccine was ineffective in a majority of trial participants, few researchers in the field were surprised. “All the animal studies pointed that way and even the phase 2 trials...suggested that it wouldn't work out—and it didn't,” says Dennis Burton (see page 380), professor of immunology at Scripps Research Institute.

Credit: Source: VaxGen, Inc.

The vaccine, which was directed against the gp120 envelope protein, elicited neither neutralizing antibodies (see page 380) nor a cellular immune response, Burton notes. “The science community is pretty angry by now because I think it was a pretty clear failure,” he says.

But with those results, VaxGen also revealed the tantalizing possibility that the vaccine conferred 78% protection in African-Americans and 67% protection in a group composed of African-Americans, Asians and other minorities. Skeptical scientists were ready with sharp pencils.

Bette Korber of Los Alamos National Laboratory questions how VaxGen derived the P (significance) value for African-Americans and the grouped minorities. “If you move the African [Americans] out, you're left with Asians and 'others' and [the results are] not significant,” she says.

In response to press reports questioning its statistical analysis, the company issued a statement saying, “the results...remain accurate as stated, and the analysis continues.” But Jim Key, VaxGen's director of communications, now says the data have not been adjusted for multi-group analysis.

Key says the next step is to find a biological explanation for the mixed results. Asked why the company went public with incomplete data analysis, Key says that VaxGen, a publicly traded company, was in a difficult position. Once the data were initially unblinded, he says, the company had to protect the information from leaking out for fear it would influence stock trading. The initial announcement of trial results was followed by an immediate drop in VaxGen's share price from about $10 to around $4.

Is it possible that a vaccine could selectively protect African-Americans? Human leukocyte antigen (HLA) genotypes could certainly affect both the transmission and cure of certain diseases, says Keith Crawford, director of clinical research at Howard University's School of Pharmacy. But Crawford and others are reserving further judgment until they see a detailed analysis. “[VaxGen] should tell people what they've done,” says Korber. “They should explain it to us.”