Many of the world's AIDS research scientists met last week in South Africa, a country that has one of the greatest rates of spread of the disease in the last few years. While these scientists heard many papers and debated many issues, what they did not hear in Durban was exciting news about an AIDS vaccine -- the only way to stop the spread of AIDS. Vaccines against viruses can produce miracles -- smallpox was eradicated from the world with a vaccine and polio is almost eradicated. Yet so far no anti-HIV vaccine has been produced. Why not?
Here are some questions I hear frequently, with the best answers I can give at this time:
Question: Focusing attention on an anti-HIV vaccine to protect against AIDS implies that we are sure that HIV causes AIDS. Are we so sure?
Answer: Yes, we know this as well as we know that smallpox viruses cause smallpox or influenza viruses cause the flu. Five thousand scientists released a declaration in Durban to this effect as a response to a few highly placed skeptics who have recently surfaced.
Q: Why do you think that a vaccine is possible when the human immune system is unable to control an HIV infection?
A: Actually, we do not know that a vaccine can be made. However, vaccines that protect monkeys against a related disease have been successful, so we believe that there must be a route to a vaccine for humans. One issue is safety -- the best monkey vaccine cannot be mimicked for human use.
Q: If a vaccine is conceivable, why don't we have one?
A: Many routes to a vaccine are under investigation, but most are years away from critical testing. The tried and true methods of making a vaccine -- like those used by Salk and Sabin to make the polio vaccines -- have not worked for HIV. Most vaccines depend on the induction of antibodies in our bodies to be effective, but HIV has hidden away its crown jewels, making them largely inaccessible to antibodies.
Our greatest hope is to induce protection by mobilizing a second arm of the immune system involving killer cells. But activation of killer cells through a vaccine is a new idea requiring much new basic knowledge. One vaccine now in human testing is based on induction of antibodies, but it is given very little hope of success. Another is far along in development, but not ready for prime time. A myriad of concepts are moving along.
Q: Is the lack of an AIDS vaccine largely the consequence of the world's biggest pharmaceutical companies standing on the sidelines because there are no huge profits to be made selling vaccines to the less-developed world?
A: Generally, industry picks up vaccine efforts after the basic science is developed in universities and research institutes. For HIV, key questions are still open and in the province of basic scientists. If the basic knowledge illuminating routes to a vaccine was there, the pharmaceutical industry would pick up the ball.
Q: Is the U.S. government underfunding the AIDS vaccine research effort?
A: The U.S. government has put more money into AIDS research than it has put into work on any other infectious agent. Ideas and effort are what's limiting here, not money.
Q: Are the best minds in the scientific community contributing to the thinking about an AIDS vaccine?
A: This has been a problem. The challenges are so great, the climate so politicized and the opportunities for career advancement so limited that many of the world's best scientists have not made the effort to contribute. However, some of the finest immunologists have recently taken a greater interest in the AIDS challenge.
Q: Realistically, when might such a vaccine be available?
A: We are not yet even certain that a vaccine is possible. It could be a decade or more before one is available for widespread use. The horror of this is that 15,000 people are being infected daily around the world. That means 50 million infections in the next decade. For comparison, 20 million Europeans are estimated to have died of bubonic plague in the Middle Ages and 18 million in the influenza epidemic of 1918.
Q: Because a vaccine is a long way off at best, what should countries do to minimize the impact of this epidemic?
A: Education, education, education. People need to know that every unprotected sexual encounter outside of a strictly monogamous relationship is a chance for transmission, as is every shared needle. Condoms, clean needles, abstinence, reduction of other infections, cleaning the blood supply, constant awareness of the danger -- all are elements of protection. Africa now, and parts of Asia soon, are fighting for their very existence as civilized countries. They must mobilize as for war, and the international community must help.
David Baltimore is chairman of the National Institutes of Health AIDS Vaccine Research Committee.