As of the end of last year, a little more than 22 million human immunodeficiency virus cases had been identified. Of those, fewer than 5 percent were in North America. And the rate at which the virus is spreading in the United States is declining - according to a recent report from the federal Centers for Disease Control - while the same is not true in many other countries.
Nearly three-quarters of all HIV infections - 15.5 million - have occurred in sub-Saharan Africa. In Uganda, half of all deaths are due to AIDS.
Some 3 million people in Southeast Asia are HIV-positive. Approximately 500,000 of them live in Thailand, where the infection rate has gone up by a factor of 10 since 1990.
The statistics are of great ethical and scientific relevance in deciding whether and where to test vaccines. The fastest way to see if a vaccine provides any sort of protection is to study a population in which the infection rate is growing quickly.
A population with a high risk of AIDS requires fewer people to be tested in order to show a preventive effect from a vaccine. That is one reason why the World Health Organization is interested in Thailand, Uganda and Brazil as locations for vaccine trials.
The ethical problems with conducting trials of new vaccines in poor nations are many, and they are especially thorny. In some nations, for instance, literacy rates are so low that it is doubtful all prospective participants would understand the nature of a test. Also, offering an AIDS vaccine might give a sense of false protection to those in the study.
Some Third World countries have almost no medical capacity for treating AIDS - making involvement in a vaccine test not so much a matter of voluntary choice as an irresistible opportunity.
Undertaking a study of a vaccine that ultimately will be sold at high prices raises questions about exploitation and equity.
Still, if it is possible to identify particular groups in poor nations that face extraordinary risks of contracting the disease and, if nothing can be done to reduce those risks, then doesn't it make sense to try a vaccine, even a risky one, on those who stand to gain the most from it? It does, but only if a few key conditions are met:
* Those chosen to participate in the trial should face extraordinary risks of getting the disease - say, sex workers in Thailand or intravenous drug users in Brazil.
* Every effort should be made to get those at high risk to stop doing whatever it is that puts them at risk, even if it threatens the speed with which vaccines can be tested.
* Every effort should be made to obtain informed consent, especially since some subjects might incorrectly presume that if they have been vaccinated they cannot acquire HIV or transmit it.
* Those in the study should know that if the vaccine works, the manufacturer will make it available at affordable prices in the nation where the study is done.
The ethics of conducting research in the midst of a raging plague are not the same as those that ought to prevail under other circumstances.
With appropriate safeguards, vaccine research in poor nations can be an act of compassion - not exploitation.