Caution urged on reading AIDS vaccine data

Shots appeared to protect black people, not others

February 25, 2003|By Jonathan Bor | Jonathan Bor,SUN STAFF

Top researchers expressed caution yesterday over a report that an experimental AIDS vaccine appeared to protect African-Americans against infection but not the broader population.

"We need to be really cautious about interpreting data on race and ethnicity," said Dr. Donald Burke, who heads vaccine research at the Johns Hopkins School of Public Health, which took part in the vaccine trial.

Factors other than race might explain why infection rates were much lower among vaccinated black people, Burke said. Possibilities include differences in geography, lifestyle or drug use, he said.

Burke was one of four scientists who analyzed data on AIDSVAX for its developer, VaxGen, a California biotechnology firm. The three-year trial involved 4,900 high-risk subjects and was the only one to progress to a full field test.

Burke noted that the vaccine seemed to raise anti-AIDS antibodies to a much higher degree in blacks than in whites, and this correlated with a lower infection rate among African-Americans. Taken together, the findings offered some hope that the vaccine is doing something and that understanding exactly what could lead to refinements and a more broadly effective vaccine, he said.

Other scientists were not so sanguine.

Dr. Paul Stolley, an epidemiologist with the University of Maryland School of Medicine, argued that the vaccine failed in the only real objective the trial was designed to measure - protecting the broad population against HIV. It succeeded in a subgroup only when scientists rooted around in the data for a glimmer of hope, he said.

"The likelihood that a vaccine will be effective in certain subgroups and not in the population at large is probably remote, though not impossible," added Stolley, a longtime critic of studies that note biological differences based on race.

He called race a false category, based on skin color but not on science, especially considering the genetic mixing of black and white over three centuries.

Even Dr. Phillip Berman, a VaxGen vice president and the vaccine's inventor, cautioned that "it's too early to conclude that the differences in antibodies is a racial difference."

A separate trial among drug-using volunteers in Thailand could shed more light on the vaccine's potential, company officials said yesterday.

The vaccine in Thailand is designed to protect against both Asian and North American strains of the virus. The company has not tested a vaccine tailored to fight a separate strain seen in Africa, which has by far the world's largest number of HIV infections.

In the trial whose results were detailed yesterday, volunteers in the United States, Canada and the Netherlands were randomly picked on a 2-to-1 basis to receive either the vaccine or a placebo. All told, 3,330 got vaccine and 1,679 a placebo.

Though doctors counseled volunteers against risky sexual practices, they expected to see infections among the volunteers because all admitted engaging in high-risk sex. Most were homosexual men, while a minority were women who had HIV-infected sexual partners.

At the end of the trial, there were 78 percent fewer infections among African-Americans who were vaccinated than among those who were not. But the numerical difference among the 314 black volunteers was quite small: nine infections among the unvaccinated, four among the vaccinated.

More than 30 vaccines have been tested since the AIDS crisis surfaced in the early 1980s, but VaxGen's was the only one to reach Phase III field trials.

Though the study results were widely anticipated, scientists are split over whether the vaccine is scientifically sound.

AIDSVAX contains a synthetic version of a protein that the AIDS virus uses to dock onto cells of the immune system. By introducing the so-called GP-120 protein to the bloodstream, scientists hope to fool the body into preducing antibodies that would defeat the AIDS virus in an actual attack.

Dr. Robert Gallo, a co-discoverer of the AIDS virus who heads the University of Maryland's Institute of Human Virology, said GP-120 vaccines were abandoned in the past because they triggered antibodies only to a specific virus raised in culture. To be practical, he said, a vaccine must protect against a variety of viruses.

"This is not a vaccine approach that was based on science," said Gallo, who also dismissed the notion that the vaccine might protect black people. "There is no scientific basis for that. I don't accept it."

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