Rethinking AIDS Strategy After a String of Failures
Thursday, November 1, 2007
DURBAN, South Africa -- Few cases of AIDS have been as closely scrutinized as that of a former South African prostitute named Beauty. Scientists know when this 40-year-old woman became infected, how her body responded and what happened as her immune system collapsed.
But when the subject turns to how Beauty might have been protected from the AIDS virus in the first place, scientists have few good leads. This fall, pharmaceutical giant Merck & Co. halted study of one of the most promising possibilities, a genetically engineered vaccine being tested on four continents, because it simply did not work.
After this latest setback, and with billions of dollars spent on research over more than two decades, scientists say they do not know when -- if ever -- a vaccine will be available in the fight against one of the world's most devastating epidemics. The news has been nearly as bad for other technological solutions, including vaginal microbicides, one-a-day prevention pills and diaphragms.
"We are really groping in the dark," said Salim S. Abdool Karim, director of the Center for the AIDS Program of Research in South Africa, in the seaside city of Durban.
The recent string of failures has sent scientists back to the lab, where, by studying the first months of infection in subjects such as Beauty, they hope to unlock some of the most enduring mysteries of HIV, the virus that causes AIDS.
But as they do, pressure is building from other experts -- some epidemiologists, physicians and scientists -- to shift attention away from technological fixes. They favor devoting more of the world's $10 billion annual AIDS spending to proven, lower-tech strategies against HIV, such as circumcising men, promoting sexual monogamy and making birth control more easily available to infected women.
"It's criminal not to put money into the things that work, and the things that work are relatively inexpensive," said Malcolm Potts, a professor at the University of California at Berkeley and former head of Family Health International, a research group with extensive experience in fighting AIDS. "We're spending money in the wrong places."
A Difficult Target
Scientists first identified AIDS in 1981. Despite more than 150 trials and steady flows of cash from the National Institutes of Health, the Bill and Melinda Gates Foundation and other major donors, there are few promising vaccine candidates, scientists say. The most anticipated, developed by NIH scientists, somewhat resembles the Merck vaccine and is due to enter trials soon.
HIV has proved a difficult target in part because it hijacks the immune system, turning the body's own defense mechanisms against it. Then the virus mutates so quickly that a tactic that works one week might be obsolete the next. Because nobody has ever been able to rid their body entirely of the virus, scientists say they do not know what a successful immune response would even look like -- making it harder to know how to provoke one with a vaccine.
Vaccines for polio, flu and measles are made from dead or weakened viruses. They generally do not cause disease, instead producing immunities that help vaccinated people battle the pathogens if encountered later at full strength.
Because scientists feared that even a dead or weakened version of the AIDS virus might cause a lethal infection, the Merck vaccine attempted to stimulate an immune response by altering a common, but much less dangerous, virus to include genetic elements of HIV. Though researchers did not expect the vaccine to prevent someone from contracting HIV, they thought it might prepare the immune system to battle a later infection, helping delay its progress to full-blown AIDS.
It didn't. The safety monitoring board for the trial called for it to be stopped Sept. 21 because the vaccine was ineffective.