In July 1762, Catherine the Great ousted her husband, Peter III, as emperor of Russia and filled the regal vacancy herself. A little over six years later, she undertook some additional risky business: getting vaccinated against smallpox.

Catherine had seen firsthand the horrors of the disease, and wished to protect herself, her loved ones, and her subjects from it. So when it was recommended that she have her son inoculated—a process that would involve cutting open his arm and directly injecting matter from an infected person’s smallpox pustule—Catherine decided to take the leap first.

“I used to reply that it would be shameful not to start with myself, and how could I introduce smallpox vaccination without setting a personal example?” she wrote to Prussia’s King Frederick the Great. “Should I remain in real danger, together with thousands of people, throughout my life, or should I prefer a lesser danger, a very brief one, and so save many people?”

Smallpox vaccination, known as variolation, wasn’t foolproof: Some people did die after failing to fight off the illness. And while India and China had embraced vaccination centuries earlier, according to The New York Times, many Europeans were still exceptionally skeptical about it. But Catherine knew that the pros of widespread inoculation outweighed the cons—and the chances of dying from variolation were much slimmer than the chances of dying from smallpox itself. In the fall of 1768, she enlisted an English physician named Thomas Dimsdale to inoculate her and her son, the future Paul I. Both recovered, and Dimsdale soon administered the treatment to other high-ranking nobles.

Though Catherine’s successful experience didn’t exactly give way to a nationwide embrace of the vaccine, she didn’t stop trying. On April 20, 1787—nearly 20 years later—she penned a letter to Count Piotr Aleksandrovich Rumiantsev, who presided over parts of what’s now Ukraine, asking that he spearhead a vaccine rollout in his region.

“Such inoculation should be common everywhere, and it is now all the more convenient, since there are doctors or medical attendants in nearly all districts, and it does not call for huge expenditure,” she wrote, translated from Russian.

Catherine then went on to detail how it should be done, directing the count to construct “lodgings for the temporary stay of those who are unable to have this inoculation done at home” and increase the salary of a certain doctor suited to the job.

As a historical record, the letter reveals just how wholeheartedly the forward-thinking ruler supported vaccination and what specific measures she took to extend the practice across Russia. As a physical artifact—bearing Catherine’s tidy script and signature—it’s worth a lot. As The New York Times reports, the letter, along with a portrait of Catherine painted by Dmitry Levitsky, just fetched $1.3 million at an auction presented by London fine art auction house MacDougall’s.

Catherine the Great wasn’t the only famous leader to endorse the smallpox vaccine before her country caught on. During his Revolutionary War days, George Washington did, too.

[h/t The New York Times]