Kennedy signs Kefauver-Harris Amendment requiring proof of drug efficacy after thalidomide crisis

President Kennedy signed the Kefauver-Harris Drug Amendments on October 10, 1962, adding an efficacy requirement to the 1938 FDCA's safety standard. Manufacturers must now provide "substantial evidence" from "adequate and well-controlled investigations" — language that formalized randomized controlled trials as the regulatory gold standard. The legislation was propelled by the thalidomide crisis in Europe, where an estimated 10,000 infants were born with birth defects; FDA reviewer Frances Kelsey had blocked U.S. approval from 1960 to 1962 by repeatedly demanding additional safety data, preventing the same catastrophe domestically.