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
History of smallpox in Mexico caused Viceroy Félix Calleja to take preventive measures like fumigations and vaccination, which were successful. There were sporadic outbreaks until 1826 when smallpox appeared in Yucatán, Tabasco and Veracruz brought by North American ships. In 1828, there were reported cases in Hidalgo, Oaxaca, State of Mexico, Guerrero, Chiapas, Chihuahua and Mexico City. Efforts to eradicate smallpox in Mexico started with Dr José Ignacio Bartolache who wrote a book in 1779 about smallpox called “Instrucción que puede servir para que se cure a los enfermos de las viruelas epidemicas que ahora se padecen en México”(Instructions that may help to cure smallpox