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Infection and immunity
Infection and immunity

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2.6  Edward Jenner, smallpox and vaccination

Smallpox begins with a high fever, fatigue, muscle pain and headaches, followed by the eruption of characteristic sores all over the body, which become filled with pus – a thick, yellowish fluid containing infected and dead cells.

Smallpox is caused by a virus, but it was not until the late 19th century that ‘infective agents’ much smaller than bacteria were shown to remain in filtered extracts from diseased animals and plants. Viruses were not ‘seen’ until the electron microscope was invented in the 1930s.

Edward Jenner (1749–1823) was a doctor in the small English country town of Berkeley (Figure 9). Smallpox was then endemic in England, causing deaths in about one-third of cases, but those who recovered were protected from smallpox for the rest of their lives. This fact was well known in India and Turkey long before this time. The practice of ‘inoculation’ (intentional exposure of children to mild cases of smallpox) became fashionable among wealthier parents in the 18th century, who hoped to protect their children from a subsequent fatal outbreak. The risk of dying from such intentional exposure was less than the risk in a smallpox epidemic, and Jenner himself had been inoculated as a child.

Figure 9  Edward Jenner, painted in about 1800 by John Raphael Smith. Note the cow and milkmaid in the background.