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How were early smallpox vaccines produced during the 19th century?

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Smallpox vaccination — smallpox Edward Jenner vaccinating his child against smallpox; colored engraving.

During the 19th century, the production of the smallpox vaccine evolved from its initial experimental stages into a more systematic commercial process.

Initially, following Edward Jenner’s 1796 discovery, vaccine material was obtained directly from individuals who had already been vaccinated. As the demand for vaccination grew and programs became more widespread—and often compulsory—this method was replaced by commercial harvesting. Vaccine producers began cultivating the virus in pustules grown on the skin of inoculated calves.1

While early efforts relied on the cowpox virus, it became apparent later in the 19th century that the original strain had been supplanted in vaccines by a different virus known as vaccinia. Whether this new strain resulted from a mutation of the cowpox virus or was an entirely separate entity remains uncertain, but vaccinia became the standard virus used for vaccine production thereafter.1