The Smallpox Boat

For centuries, the smallpox disease claimed the lives of huge numbers of people around the world. In the early 1700s, the famed French writer and philosopher Voltaire estimated that 60% of the population of England contracted smallpox at one point or another, and 20% of the total population died from the disease. But today, the disease is, thankfully, effectively eradicated. That is because of a vaccine developed by an English physician named Edward Jenner in 1796. It took nearly two hundred years, but Jenner’s vaccine ultimately made it around the globe; the last known case of the disease dates back to 1978. That’s a long time, but it could have been longer — if it weren’t for the controversial idea of a Spanish doctor named Francisco Javier de Balmis.

Jenner’s critical discovery was that exposure to pus from cowpox — a disease which is similar to smallpox but much milder — would immunize a person against smallpox. By 1800, word of his discovery spread through most of Western Europe, and later, to the Americas. Demand for the vaccine quickly followed. But the vaccine required a live cowpox virus, and the world of the early 1800s didn’t have airplanes or any other way to quickly transport a live cowpox strain across the Atlantic, and advances in medical storage similarly didn’t allow for the vaccine to be put on a ship and transported west over a weeks-long voyage.

In 1803, Dr. Balmis came up with the solution: two dozen or so orphans.

Dr. Balmis noted that the cowpox virus could easily be transmitted from person to person — the pus from an infected person, if introduced into a previously unexposed person, would cause cowpox to spread. And that, ultimately, was a good thing, because cowpox exposure inoculated the infected against smallpox. So, Dr. Balmis correctly concluded that if you put someone infected with cowpox on a ship and sent them across the ocean, that person could carry the smallpox vaccine in his or her blood. The only problem with the plan is that the person’s immune system would fight off the cowpox virus long before he or she arrived in the Americas — and therefore, the vaccine would not longer be viable upon arrival.

So Dr. Balmis expanded on the idea. It wasn’t enough to have that one patient sail across the ocean; Dr. Balmis needed a bunch of unexposed people to join the trip. Along the way, pus from the initial cowpox patient would be introduced to a second, and then from the second to a third, and so on, with some redundancies built in to account for unforeseen problems. Dr. Balmis’ theory, effectively, was to daisy-chain the cowpox virus across the Atlantic through the blood of passengers on-board.

Of course, Dr. Balmis had difficulty finding volunteers for an obviously dangerous trip — trans-Atlantic transportation wasn’t the safest thing to begin with — so he found a group of people who would have trouble refusing: orphans. With the blessing of King Charles IV of Spain, Balmis, a half-dozen or so various medical assistants, the matron of the orphanage, and 22 orphan boys ages eight to ten set across the Atlantic in an effort to, in a sense, save the world.

The mission, now known as the Balmis Expedition, was successful. The expedition introduced the smallpox inoculation to various parts of Central and South America, and it spread over land to North America as well. As for the orphans? Per one source, they survived the voyage and settled in Mexico, under the guise of the church.

Bonus Fact: Because smallpox has been eradicated (except for some strains in government laboratories), people generally do not receive the smallpox vaccine any longer. But if you’re an American, there’s a vaccine waiting for you if need be. According to the Centers for Disease Control and Prevention, “the United States has a big enough stockpile of smallpox vaccine to vaccinate everyone in the United States in the event of a smallpox emergency.”

From the ArchivesBefore Salk: Stories of the polio vaccine.

RelatedA well-regarded book on the eradication of smallpox.