By John Carey
For all our fears about bioterrorists unleashing killer plagues, nature has once again proven to be a greater danger. Severe acute respiratory syndrome (SARS) has infected 3,200 people in 23 countries, killing more than 150. The economic costs are $30 billion and rising, according to the World Health Organization. And just when health authorities thought the disease might be contained in North America, more than 30 suspected new cases were discovered in Toronto.
If authorities can't stamp out SARS in Canada, the prospects are grim for rural China and other regions that lack modern hospitals and public-health systems. Many infectious-disease experts now fear that SARS will march relentlessly around the world. Respiratory diseases that spread from people to people are "virtually unstoppable," warns Dr. Thomas Monath, former top virologist for the U.S. Army Medical Research Institute of Infectious Diseases and now research chief at vaccine maker Acambis PLC.
U.S. Army researchers, among others, are rushing to test thousands of drugs to see if any can knock back the virus. But viruses are notoriously difficult to attack in this fashion. The only credible solution is to mount a massive effort to develop a vaccine. Such an effort might cost several hundred million dollars. But that's small change compared with the economic havoc that would be caused by repeated outbreaks. And the effort might provide a template for responding to future emerging diseases or bioterrorist attacks. "If we believe SARS is likely to recur, a vaccine would be the best strategy," says Stephen S. Morse, infectious-disease expert at Columbia University.
Health & Human Services Secretary Tommy G. Thompson has already met with pharmaceutical companies to talk about how a vaccine could be produced. The idea is to first try an old-fashioned method: Grow big batches of the virus, kill it with formaldehyde, and inject the dead virus into animals -- and eventually people -- in hopes of triggering an immune response capable of repelling the living microbe. Because similar vaccines against bugs related to the corona virus that causes SARS succeed in animals, "the killed virus may well work," says Stephen Albert Johnston, professor of medicine and biochemistry at the University of Texas Southwestern Medical Center.
Given how infectious SARS is, though, growing large quantities isn't easy or safe. But there are also promising new approaches. In a project originally funded by the Defense Dept. to combat bioterrorist attacks, Johnston's group at Texas has created a way to break down a new infectious agent into small components. Then the scientists can quickly test the components to find out which one stimulates the best immune response. The group has made vaccine candidates against a number of bioterror agents and is now preparing to tackle SARS. One crucial step -- finding an animal that can be infected with the virus and thus can be used to test vaccines -- has already been achieved in the Netherlands.
Normally, vaccines require years of clinical trials to win Food & Drug Administration approval. But the government could put a SARS vaccine on a faster track, using a recent regulatory change aimed at speeding development of drugs and vaccines against bioterror agents. In those cases, the FDA is willing to accept a vaccine's efficacy based mainly on animal trials -- as long as it's safe in humans. Washington could further speed vaccine-research efforts if it promised to purchase the resulting vaccines, and to limit producers' liability from vaccine side effects.
Some epidemiologists believe the U.S. can snuff out SARS for now. But the disease almost certainly will continue to lurk in China, erupting periodically and spreading. If it gains a foothold in Africa, India, or South America, it's virtually guaranteed to come back again and again. The U.S. government needs to step up now with funding and a legal framework for a major vaccine effort. It's the only way to inoculate society against emerging diseases. Carey covers science and medicine from Washington.