Anthrax vaccines known to result in far less scarring, and greatly reduced mortality, in comparison with the naturally acquired disease. The English physician Edward Jenner (1749–1823) had also discovered (1796) the process of vaccination by using cowpox to give cross-immunity to smallpox and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference between smallpox vaccination and anthrax or chicken cholera vaccination was that the weakened form of the latter two disease organisms had been "generated artificially", so a naturally weak form of the disease organism did not need to be found. This discovery revolutionized
1947 New York City smallpox outbreak Bar had developed a fever and pronounced rash. He was admitted to Bellevue Hospital, but because of the rash was transferred three days later to Willard Parker Hospital, a communicable disease hospital also in Manhattan. On admission to Willard Parker, the differential diagnosis was drug reaction (since Le Bar had reported taking proprietary headache powders and aspirin), erythema multiforme, Kaposi's varicelliform eruption, and smallpox. However, because Le Bar had a smallpox vaccination scar, an atypical rash, and no history of exposure, smallpox was immediately ruled out. A biopsy of the skin lesions did not reveal the Guarnieri bodies characteristic of