The Laws of Immunity.

by Kenneth W. Krause.

[Notable New Media]

Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer.  Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes frequently to Skeptic as well.  He can be contracted at

So how did humans overcome smallpox? Well, that’s an interesting story.

Toward the end of the 18th century, Edward Jenner noticed that, after recovery from infection with the cowpox virus (vaccinia), milkmaids rarely contracted smallpox. Importantly, vaccinia is very closely related to variola, the smallpox virus.

Edward Jenner

Edward Jenner

So in 1796, Jenner extracted fluid from the pustules on one Sarah Nelmes, suffering from cowpox, and injected it into a healthy James Phipps. After Phipps recovered from a mild case of cowpox, Jenner then intentionally injected him with fluid from the pustules of a smallpox patient. Phipps didn’t develop signs of smallpox infection because the cowpox virus (and the process of “adaptive immunity”) had protected him.

Jenner’s methods obviously wouldn’t pass ethical muster today. But such practices were not uncommon in the 18th century, and understandably so. Smallpox was responsible for more human deaths than any other infectious agent.

Regardless, smallpox vaccination became common in Europe and infection rates dropped dramatically by 1820. In 1853, the UK required every healthy child to be so vaccinated within 3 or 4 months of birth. By 1980, smallpox was formally declared eliminated worldwide.

Read more about the subject generally in William Paul’s new book, Immunity (Johns Hopkins University Press 2015).



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