San Francisco Chronicle - THURSDAY, December 3, 1992
Alex Barnum, Chronicle Staff Writer

The National Institutes of Health said Tuesday it will begin testing, at five medical centers, the two most promising vaccine candidates on 320 volunteers, including gay men who practice high-risk behavior, intravenous drug users and heterosexual partners of infected people.

Both vaccines are genetically engineered versions of a protein found on the virus' surface. In smaller, preliminary trials, both were found to be safe and to prompt the body to produce antibodies that neutralize the virus in a test tube.

The vaccines were chosen from among six candidates because they are made from strains of the virus that are most prevalent in the United States and because they were able to provoke an immune response against other strains of the virus.

One of the vaccines was developed by Genentech Inc. of South San Francisco; the other by a joint venture between Emeryville-based Chiron Corp. and Ciba Geigy Corp.

The trial is not intended to measure whether the vaccines prevent infection. Instead, it is meant to determine whether they produce immune responses in people who are the most likely candidates for an AIDS vaccine.

But by including high-risk individuals for the first time, the trial raises one of the essential dilemmas of developing an AIDS vaccine: To measure how well it works, it is necessary to test it on people who are likely to be exposed to the virus -- which opens up the question of whether it is ethical to do so.

A primary concern is that if volunteers believe a vaccine has immunized them against infection, they might engage in higher risk behavior. So, as part of the trial, participants will be counseled not to do anything that could expose them to the virus.

"We're not trying to use anybody as a guinea pig," said a spokeswoman for the National Institutes of Allergy and Infectious Diseases, which is sponsoring the trial. "We expect that they will not continue to practice high-risk behavior, although we can't be sure."

The reality is that some will engage in unsafe practices: Researchers admit that their ability to determine whether the vaccine works will be dependent on volunteers failing to practice safe sex and exposing themselves to the virus.

In a trial to determine whether a vaccine prevents infection, researchers would compare the the rate of infection among people who received the vaccine against those who did not.

But for statistically meaningful results, such a trial would have to be enormous, with as many as 10,000 healthy, high-risk volunteers. One of the goals of the current trial is to determine the feasibility of such a large-scale test. Large-scale trials have divided the medical and scientific communities.

One issue is the establishment of an acceptable rate of prevention. Some have argued that even if a vaccine reduces the rate of HIV infection by only 50 percent, it should be considered a good first step and be made available to high-risk individuals.

Others say that that figure is too low and call for a higher threshold of effectiveness closer to those of other vaccines. At the high end, the hepatitis B vaccine is 80 percent effective, while at the low end, flu vaccines are only about 60 percent effective.

Some question whether a larger trial is appropriate at all.

Some say it is premature because evidence of vaccine effectiveness to date is so meager. Some say that an AIDS vaccine could even harm volunteers by ultimately lowering their defenses against infection. And some doubt that AIDS ever will be controlled by a vaccine.

Always watch for outdated information. This article first appeared in 1992. This material is designed to support, not replace, the relationship that exists between you and your doctor.

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 1992. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .