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Why did variolation still spread smallpox and sometimes cause deaths?
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smallpox
Edward Jenner vaccinating his child against smallpox; colored engraving.
Variolation involved infecting a healthy person with material taken from the sores of someone suffering from a mild case of smallpox. While the procedure was intended to induce a less-dangerous form of the disease, it was inherently risky because it utilized the actual smallpox virus.12
The practice could lead to deaths and further outbreaks for two primary reasons:
- Development of full-blown disease: Recipients of the procedure could develop a severe, full-blown case of smallpox rather than the intended mild form, which sometimes resulted in death.2
- Transmission to others: Because the procedure involved the live virus, individuals who were variolated could unwittingly spread the fatal form of the disease to others, effectively acting as a source of infection during the period they were ill.23
Due to these significant dangers, the practice was eventually opposed by most physicians and replaced by Edward Jenner's safer method of vaccination using cowpox, which ultimately led to the global eradication of smallpox.2