Last fall, after trials of a promising AIDS vaccine from Merck Co. came back with alarming results, they were canceled. Health experts knew the significance of that, but when The Post reported on the enormity of the situation last month, many were astounded. Not only did the vaccine not protect trial participants from infection with HIV, the virus that causes AIDS, but it also appeared to make them more susceptible to contracting the disease. At least a half-dozen other trials were stopped or put on hold. The Merck disappointment was branded as a "catastrophe" by one scientist and as setting the race for a cure "back to square one" by others. The hyperbole is understandable, but some perspective is in order.

The AIDS epidemic has cut a destructive path across entire continents and all socioeconomic, racial and ethnic groups. Men, women and children have succumbed to the disease. By the end of 2007, 26 million people around the world (566,000 in the United States, as of 2006) had died of AIDS. The number of people infected with HIV stands at 33 million (1.1 million in the United States). Americans and people around the world have agitated against government indifference and public apathy to instill a sense of urgency to develop medicines that would ease the suffering of those with the disease and to ultimately find a vaccine.

Finding a vaccine is neither easy nor fast, however, and failure of human vaccine trials is common. For instance, since World War II, there have been more than 20 failed tests for malaria, which has no vaccine. The polio vaccine took scientists 47 years to find; measles, 42. HIV was discovered only 25 years ago. There's still much that isn't known about the virus or AIDS. So what might look like a devastating failure to the public could be a steppingstone to advanced medications and an eventual cure. There was a series of questions that the Merck scientists were looking to answer, and they answered them. The answers just weren't the ones the scientists were hoping for.

The director of the National Institute of Allergy and Infectious Diseases, Anthony S. Fauci, convened a one-day gathering of the world's premier AIDS scientists at the National Institutes of Health last month to reassess priorities. The race for a vaccine continues. But the scientists rededicated themselves to conducting more basic research. That approach is prudent. While we share the impatience of those who want a cure, that solution will require better science.

"" The Washington Post