Miami Herald - July 11, 2002
Fred Tasker, ftasker@herald.com

AidsVax, in the last stage of clinical trials, is the only AIDS vaccine now at this late stage of development. If approved by the Food and Drug Administration, it could reach market by 2005. The trials' results are expected next year and 2004.

One of the major issues: Will a sufficient percentage of those inoculated be protected from acquiring HIV, the AIDS virus?

The California research firm behind the vaccine, VaxGen, says yes.

It has formed a $120 million venture with South Korean investors to create production facilities that by 2005 could be turning out 200 million doses a year, said company president Donald Francis.

"Based on data so far, [Francis] is very confident it will be efficacious," said company spokesman Jim Key. "The question is, how efficacious?"

"Even a first-generation vaccine that was only 25 percent effective could break the back of the global epidemic," said Dr. M.T. Isbell of the International AIDS Vaccine Initiative. "But only if it were available to everybody who needs it."

About 40 million people worldwide live with AIDS or HIV, and projections call for 45 million more people to be infected by the end of the decade.

A cost-benefits analysis by UNAIDS and other world organizations concluded that, if a vaccine were 90 percent effective, its best use would be to create 690 million multi-dose courses to vaccinate 22 percent of all the 15- through 49-year-olds in the world, and 69 percent of that age range in high-risk areas such as Africa.

A vaccine that was only 30 to 50 percent effective might be made in 260 million multi-dose courses, to treat smaller percentages of the same age groups. It would need fewer doses because some at-risk populations might use condoms.

"It shows that there would be a tremendous market even for moderately successful vaccine," said Marie Louise Chang of the World Health Organization.

But even if first-generation HIV/AIDS vaccines succeed, they are not expected to be as effective as todays vaccines against polio, measles or hepatitis.

Several experts here said they may immunize only 25 to 30 percent of those who take them, be effective against some HIV/AIDS strains but not others, and be of questionable duration.

An all-purpose vaccine probably will come only after years more of research, if ever, experts say.

That research is under way. Drug companies and university scientists at the conference are presenting data on a dozen or more vaccine trials -- some still in test tubes, some with chimpanzees, some with humans.

AidsVax is in its critical, final Phase III trials with 5,400 healthy volunteers from the United States, Canada, the Netherlands and Puerto Rico, in scores of clinics including three in South Florida.

The volunteers are 94 percent men who have sex with men and 6 percent heterosexual women with high-risk sexual behavior, such as having unprotected intercourse.

The vaccine also is being tested on 2,500 injecting drug users in Thailand. In each trial, half the volunteers get the vaccine, half get a placebo.

In Phase I and II human trials by VaxGen, the vaccine was shown to be safe and to produce antibodies in almost all who received it.

AidsVax works by inducing the immune system to produce antibodies to the condition it is fighting. The antibodies attach to the protein on the virus surface that HIV uses to fuse through and infect healthy cells. If the vaccine can stop the virus from attaching to the healthy cells, it will have worked.

Another study involves 1,300 volunteers at 70 U.S. clinical sites, including one at the University of Miami. The study, sponsored by the drug manufacturer Merck, includes infected and noninfected people.

In one part of the study, 48 uninfected volunteers were injected, some with the vaccine candidate, others with a placebo. After 30 weeks, between 67 and 78 percent of those who got the vaccine showed positive immune responses.

The study includes infected people to see whether the vaccine can stimulate the immune system so it can control the virus effectively.

In being given to infected people, HIV/AIDS vaccines are unlike others.

"There are two ways you can use a vaccine," said UM AIDS researcher Margaret Fischl. "One way is to give it as a prevention, to people at risk but not infected, hoping it will prevent infection. The other way is using it in therapy for infected patients, adding to the potency of treatment to get rid of the virus."

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