The Cincinnati Children's Hospital Medical Center in Ohio, and the Harbor-UCLA Medical Center in Southern California will undertake landmark clinical trials of the smallpox vaccine. The tests, the first ever of the smallpox vaccine on children using modern scientific technology, are being done to establish suitable child dosages in the event that mass vaccination is needed because of a bioterrorist attack. Prior to the disease's eradication in 1980, the vaccine had been successfully administered to children for many years, but controlled trials of it had not been performed. Researchers plan to use the Dryvax vaccine--a mainstay in the National Pharmaceutical Stockpile and the same one used during the global eradication efforts in the 1960s and 1970s, and also the same one used in adult clinical trials that began last year testing the effectiveness of a diluted dosage of the vaccine. Doses to be used in the children are from stock prepared by the New York City Health Department over 40 years ago, and researchers hope to find out how diluted the dosages can be in children and still be effective. Researchers believe that modern medical knowledge may make Dryvax's risk factors less of a problem; the vaccine is developed from a live virus that has caused encephalitis and brain damage in some cases as well as carrying a 1 in 1 million risk of death as studies in the 1960s found. The trial protocol and the age of the children in the trial have yet to be finalized by the National Institute of Allergy and Infectious Diseases and the Food and Drug Administration.