A recently unearthed letter from Admiral Horatio Nelson to his mistress, Lady Emma Hamilton, written in 1801, reveals Nelson recommending that their six-month-old baby daughter be given the smallpox vaccine developed by Edward Jenner just three years before.

It is difficult to overstate what a scourge smallpox was in previous centuries. The case-fatality rate varied from 20% to 60% and left most survivors with disfiguring scars. The case-fatality rate in infants was even higher, approaching 80% in London … during the late 1800s.

Prior to Jenner’s vaccine, the only defense against the disease was a technique called variolation in which material from smallpox sores was given to people who had never had smallpox by either scratching the material into the arm or inhaling it through the nose. With both types of variolation, people usually went on to develop the symptoms associated with smallpox, such as fever and a rash. However, fewer people died from variolation than if they had acquired smallpox naturally. 

While fewer people died from variolation, an estimated 2-3% did succumb. The deaths included King George III’s son Octavius when he was just four years old. 

Jenner’s vaccine, developed from cowpox, was far less risky but was new enough so that it greeted by many with skepticism. Nelson was more open-minded. In the letter he wrote:

“Yesterday, the subject turned on the cow-pox. A gentleman declared that his child was inoculated with the cow-pox; and afterwards remained in a house where a child has the small-pox the natural way, and did not catch it. Therefore, here was a full trial with the cow-pox.”

He went on to note that the effects of Jenner’s vaccine were far milder than variolation. “The child is only feverish for two days; and only a slight inflammation of the arm takes place, instead of being all over scabs.”

Despite his recommendation that his daughter be vaccinated, Nelson leaves the final decision to her mother writing, “But do what you please.”

“You’re never out of my thoughts,” he confesses, signing the letter “ever, forever, yours, only your Nelson.”

Thanks to Alaric Bond for contributing to this post.