tens of millions of tuberculosis ( tb ) patients worldwide are facing a serious risk to their lives. They may succumb to the disease even before medical science comes up with a better vaccine or more effective antibiotic treatments. Barry Bloom of the Albert Einstein College of Medicine in New York told a gathering of scientists in Chicago that the inherent slowness of tb vaccine trials means that doctors will not have an effective global immunisation against the disease for another 30 to 40 years. By then we could witness another 80 million deaths, he says.

Given this lag, most tb experts agree that there is an urgent need for better treatment. "We're ready now to look at a new aggressive approach to preventive therapy,' says Richard O'Brian of the Atlanta-based us Center for Disease Control and Prevention. Such therapy is usually given to patients exposed to the tb bacterium