About Jenner Analytics

It is hard today to picture how much smallpox was feared. In the 18th century it killed an estimated 400,000 people in Europe every year, and in cities such as London it was a common disease of childhood. Between 20% and 60% of those infected died; among infants the rate approached 80% in London and 98% in Berlin. Most survivors were left with disfiguring scars, and smallpox caused about a third of all blindness. Even in the 20th century, before it was eradicated, it killed an estimated 250–500 million people.

The best protection on offer was variolation: deliberately infecting a healthy person with material from a smallpox sore, which was usually far less deadly than catching the disease naturally. Jenner himself was variolated as a boy of about eight, an experience said to have affected his health for the rest of his life. Variolation was far from safe: roughly 1–3% of those treated died, and they could pass smallpox on and start new outbreaks.

Others, such as the farmer Benjamin Jesty in 1774, had already used cowpox to protect their families. Jenner's lasting contribution was to put the idea to the test. Weeks after inoculating James Phipps with cowpox, he exposed the boy to smallpox material, and no disease followed. He repeated the test on further subjects and, when the Royal Society declined his first report in 1797, published 23 cases himself in his Inquiry of 1798: early, careful, systematic testing that showed vaccination to be effective and far safer than variolation.

That evidence carried the argument. By 1800 vaccination had reached most European countries, and in 1840 Britain banned variolation and offered vaccination free of charge. Vaccination went on to become an essential part of the effort that finally rid the world of smallpox.