Baltimore to head new vaccine panel.

Ontario, who was the principal investigator in the CAPRIE study, says that "When they started this study in 1988, there was clear evidence from a number of published studies that antiplatelet drugs, particularly aspirin, prevented stroke ... in these patients." The 1649 people in the placebo group were unnecessarily exposed to a higher risk, he says. Erasmus's Koudstaal says that there may have been room to doubt aspirin's efficacy at the beginning of the trial. But later studies, such as the 1991 Swedish Aspirin Low-dose Trial ( SALT) and the "aspirin papers," a series of meta-analyses published in the British Medicat}oumal in 1994, "convincingly proved" that aspirin worked, he says, and should have been reason to stop the placebo arm of the trial. Yet, the study continued until March 1995. "It was probably a mistake at the time," adds Charles Warlow, a neurologist at Western General Hospital in Edinburgh, U.K. "I personally wouldn't have put people in the trial. But there are many perfectly respectable people who did. People vary in what they regard as definite evidence." Verhorst and Lowenthal dismiss these criticisms, arguing that the efficacy of aspirin, as well as the optimal dosage, was not known when the trial started. Says Verhorst: "The study was submitted to ethical committees in every center. If 59 ethical committees approve, then there is no ethical problem." And Lowenthal says that the trial was monitored by a central ethics committee, which discussed the study each year. It reported in 1995 that use of placebos was justified because of doubts about aspirin's efficacy and NEWS & COMMENT