History of Disease

Smallpox Vaccine

In the late seventeen hundreds, the English country doctor Edward Jenner noticed that dairymaids, who had contracted cowpox seemed to be protected from smallpox. (15:57) In 1796, Jenner experimented by infecting a boy with cowpox pus, then later with smallpox pus. The boy did not contract smallpox. (15:57)

Through this experiment he demonstrated that infecting a person with a mild or harmless virus would strengthen immunity to a similar disease-causing virus. (15:57) He called this pus “the Vaccine Virus” – the word vaccine is derived from the Latin word for cow. (15:57) Jenner called this infectious material vaccine, and the procedure came to be called vaccination. The practice of vaccination became widespread in Europe.

The material Jenner used for his vaccine probably contained cowpox virus, a virus related to variola but not as virulent. At some time during the nineteenth century, the virus used for smallpox vaccination ceased to be cowpox and changed to vaccinia. (19:15) Vaccinia is in the same family as cowpox and variola, but is genetically distinct from both. Neutralizing antibodies induced by vaccinia vaccine are cross protective for other Orthopoxviruses, such as monkeypox, cowpox, and variola viruses. (22:V6:4)The origin of vaccinia, and how it came to replace cowpox virus in the vaccine is not known.

Mass vaccination became more achievable with one of the most significant events in the history of smallpox vaccination, the growth of the vaccine virus on the flank of a calf in Italy, which lead to the main method for vaccine production.

With the use of vaccine produced from the flank of cows, most of Europe became smallpox free after WWI. The virus for the vaccine was grown on the skin of calves, sheep and water buffalo. Material from the lesions on these animals was harvested before the pustules formed scabs in order to obtain the highest viral load. This was then ground into a pulp and mixed with 40 to 60% glycerol. (22:V6:8) After WWII endemic transmission was completely interrupted in Europe and North America. With the development of a freeze-dried vaccine that was more stable in higher temperature and humidity climates, vaccine was available for wider use throughout the world.

The vaccine currently available in the United States was prepared in the early 1980s from calf lymph with a seed virus derived from the New York City Board of Health strain of vaccinia. (19:15)

 
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