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To practically no one’s surprise, the first test of an AIDS vaccine has failed. That the outcome was widely predicted — and even anticipated — must not deter future efforts to develop a vaccine. AIDS is one of the worst scourges humanity has suffered to date, and a combination of economics and demographics ensures that it will get worse. Few challenges are more difficult or more urgent.

Acquired Immunodeficiency Syndrome, now known to the world as AIDS, first emerged about 20 years ago. In two short decades, it has claimed about 25 million victims. There are 13,000 new AIDS infections every day, 2,000 of them children under the age of 15. Some 8,500 people die every day of the disease. By 2010, there will be 20 million AIDS orphans in Africa alone. The United Nations estimates that AIDS will kill 46 million people this decade alone in the 53 worst affected countries. The death toll is predicted to rise to 278 million by 2050.

The task of beating the disease is compounded by the grim economic reality of its pathology. Ninety-six percent of the 36.1 million people currently living with the disease’s precursor, HIV, live in developing countries where any medical treatment is a luxury. The stigma associated with the disease discourages governments from addressing the problem head on. That failure alone facilitates its spread. The sheer number of the sick and the dying is slowing economic development and compounding the economic and human cost of infection. A cocktail of drugs has been developed that has reduced AIDS deaths by as much as 75 percent, but the treatment costs thousands of dollars, putting it beyond the reach of all but a tiny proportion of the population in the worst-affected areas.

The high cost of treating the disease led researchers to pin their hopes on a vaccine that would prevent its spread. Last month, the first test results were in, and the worst fears were confirmed: The vaccine failed to protect recipients from infection with the virus that causes the disease.

The vaccine was developed by VaxGen, a small American biotechnology company. The trial took place at 59 sites over three years and used 5,400 volunteers, mostly from the United States, but additional participants came from Canada, Puerto Rico and the Netherlands. The test population consisted mostly of men, none of whom were infected with HIV when the trial began. Typically, a vaccine has to work in 70 percent of cases to be considered effective. VaxGen had hoped the vaccine would prevent 30 percent of infections. Yet even with those low expectations, the tests were a disappointment. In the overall population of participants, 5.8 percent of those who received the placebo became infected, compared with 5.7 percent of those who received the vaccine. The difference is not statistically significant.

There was one anomaly in the results: Among black, Asian and other minorities, the rate of infection was only 3.7 percent in the vaccinated group, compared with 9.9 percent in the placebo group. That indicated that the vaccine cut infections in that group by 66.8 percent, a respectable outcome. Researchers caution that the test group was small — only about 500 patients — even though there was less than a 1 percent chance that the findings were the result of chance. They also caution that they cannot explain why there are different ethnic responses to the vaccine. A second test that uses Thai volunteers is currently underway; those results will be available later this year.

While VaxGen conceded that the results were disappointing, public health officials have put the best possible face on the trials. The U.N.’s leading expert on AIDS vaccines, Dr. Jose Esparza, called the tests “the first demonstration of protection in humans” and said the results “should give encouragement to all vaccine developers.” Other researchers were more skeptical.

Science still does not understand how HIV and AIDS viruses work. We do know that HIV mutates quickly and that there are a number of strains. VaxGen’s vaccine was designed to work on the subtype found predominantly in rich countries; it would have little effect in Africa, where the pandemic is doing the most damage.

The clash of economic and demographic reality is deadly. There is little business incentive for companies to spend money on a drug when most of its target recipients cannot afford to pay for it. Market failure should have predicted the scientific failure. Scientific uncertainties could work in favor of disadvantaged victims, however; the diversity of strains means that research designed to help rich victims (who could pay) might yield results for the poor. Alternatively, governments could decide that efforts to fight AIDS demand substantive attention and support. Rhetoric notwithstanding, that is as likely as VaxGen’s success on its very first try.

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