AIDS vaccine: time for human tests?

AIDS vaccine: Time for human tests?

Four years after the AIDS virus was firstidentified, researchers are beginning to embark on human trials of vaccines against the deadly disease. As of March 30, according to a Food and Drug Administration spokesman, three research groups in the United States had applied to the FDA for permission to test their candidate vaccines in the first phase of human trials, which is designed to test vaccine safety in a few people. And two weeks ago, a French scientist reported that he had injected himself and other volunteers in Zaire with one experimental AIDS vaccine (SN: 3/28/87, p. 198).

"I think it is virtually certain that therewill be initial [U.S.] clinical studies [during] this calendar year,' the FDA's Gerald V. Quinnan told reporters last week at an international AIDS vaccine workshop held at the National Institutes of Health in Bethesda, Md.

But while testing in human subjects isviewed by some as a milestone in AIDS vaccine research, scientists caution that a safe and effective vaccine--assuming one is indeed found--is years, if not decades, away. Moreover, not all researchers agree that human studies are yet warranted.

One of the most hotly debated questionsat the workshop was whether researchers should have to show that their vaccine protects chimpanzees against AIDS infection before any--but especially large-scale efficacy--human studies are undertaken. Chimps are the only nonhuman animals that can be infected with the virus, although they have yet to develop full-blown AIDS symptoms. So far, chimps inoculated with some vaccines have produced antibodies and shown other immune responses to the AIDS virus. But no studies are known to have shown that a vaccine has actually protected chimps against an infection.

Quinnan and others argue that humantrials of vaccines should not be barred on this basis alone, because the chimp immune system may not be a good model for that of humans. Moreover, they note, these chimps have been given a large intravenous dose of the AIDS virus, whereas humans are infected with AIDS through sexual and other kinds of contact. But other scientists say they'd be uneasy about going ahead with full-scale human tests before protection is shown in chimps. Most workshop participants agreed that the chimpanzee's role in vaccine development will be an evolving question. Still, asked one scientist, "Once we start down the road of giving vaccines to humans, how far can we go without knowing that they are efficacious? The public pressure to push on will be considerable.'