An Inquiry into the Causes and Effects of the Variolae Vaccinae (with Further Observations and A Continuation of Facts)

Summary

Edward Jenner's Inquiry into the Causes and Effects of the Variolae Vaccinae, published in London in 1798, is the founding document of vaccination. Smallpox then killed or scarred a large share of every generation in Europe. The only protection was inoculation, or variolation: deliberately giving a person a mild case of smallpox from the matter of a smallpox sore, which was risky and could spread the disease. Jenner, a country doctor, had heard dairymaids say that people who caught cowpox, a mild disease of cows' udders that produced sores on milkers' hands, never took smallpox. He gathered cases of farm workers who had had cowpox years before and then failed to react when inoculated with smallpox. In May 1796 he took matter from a cowpox sore on the hand of the dairymaid Sarah Nelmes and inserted it into the arm of a healthy boy of about eight, James Phipps (named in Jenner's later writings; the Inquiry calls him simply a healthy boy). Weeks later he inoculated the boy with smallpox matter, and no disease followed. In 1798 he passed cowpox from arm to arm through several more children and again showed that they resisted smallpox. The Inquiry sets out twenty-three numbered cases with plain descriptions and hand-coloured plates of the sores. Jenner also offered a theory, now known to be mistaken, that cowpox came from a disease of horses' heels called 'the grease'. In Further Observations (1799) and A Continuation of Facts and Observations (1800) he answered critics, described failures caused by 'spurious' cowpox or matter taken too late, and reported the rapid spread of the practice. He ends by congratulating his country on an antidote able to rid the earth of smallpox. The word vaccine comes from vacca, Latin for cow. In 1980 the World Health Organization declared smallpox eradicated.

Top Lessons

• Observation and testing

  Jenner took a piece of folk wisdom seriously but did not stop there: he collected cases and then tested the claim by experiment. Good science often begins by listening carefully and continues by checking.

• Risk and responsibility

  Jenner deliberately exposed a child to smallpox matter. Variolation was common practice then, but his experiment raises questions that modern rules on research with children try to answer.

• Being wrong in part

  Jenner was right about cowpox and smallpox but wrong about the horse disease called the grease. Scientific discoveries can be true in their core and mistaken at the edges.

• For the Christian reader

  Jenner was a churchgoing Anglican who saw his discovery as a gift to the human family. Christians have long seen healing as a way of loving one's neighbour, and the global work that ended smallpox shows how knowledge shared freely can serve the poor everywhere.

Verified Quotes

Medical Lens

The founding text of vaccination: a model of case-based clinical reasoning, and a starting point for discussing consent and research on children.

• An Inquiry, Case XVII

  The 1796 experiment on a healthy boy, later named as James Phipps.

• A Continuation (1800)

  The spread of vaccination and Jenner's prediction of eradication.