MARY LOUISE KELLY, HOST:
Twenty-two - it's the number of diseases we are able to vaccinate against in the U.S. A vaccine exposes us to something that can kill us or sicken us with the goal of protecting us from illness. Now, where did that idea originate? Sarah Gonzalez with our Planet Money podcast has the 2,000-year-old story of the first vaccine.
SARAH GONZALEZ, BYLINE: As long as humans have been around, humans have been getting sick and dying. But some humans have been getting sick and not dying. They were immune, and people noticed, like the ancient Greek historian Thucydides. He wrote in 430 B.C. about a plague, probably smallpox.
JOSEFA STEINHAUER: And he noted that the few individuals who recovered from the disease could tend to the sick without becoming reinfected.
GONZALEZ: Josefa Steinhauer is a molecular biologist at Yeshiva University. She says smallpox stuck around for thousands of years, killed many millions. And in the Middle Ages, Chinese physicians thought, what if we could manufacture immunity - cause it?
STEINHAUER: So they're going to collect scabs from a person with a mild case. Then you're going to ground them up into a powder, pack the material into a pipe and puff the whole concoction into an uninfected person's nose.
GONZALEZ: This whiff of smallpox was the first vaccine. We just didn't have that word yet - vaccine. And knowledge about manufacturing immunity spread, just like the virus itself, along the Silk Road. That is where an English woman sees a different approach to the nose pipe thing - Lady Mary Wortley Montagu. It's the early 1700s, and she sees potential.
STEINHAUER: This is very personal for her because she was very famous for being beautiful, and smallpox ravages her beauty, destroys her face.
GONZALEZ: She lost her eyelashes. It was awful for her. The king, George I, he hears about it. He's skeptical but agrees to sponsor an early clinical trial.
STEINHAUER: Who should they use as their trial guinea pigs? What about people on death row?
GONZALEZ: They sprinkle smallpox into the cuts of six death row inmates at Newgate prison in 1721. If they survived, the king would pardon them, set them free. All six prisoners survived, all six were released, and all six became immune to smallpox. After this, all the royals sign up. It's a rich person thing. But it wasn't entirely safe yet. Some people died from the exposure. The next breakthrough came from looking at the problem through the eyes of a cow. Cows would sometimes get these pustules on their udders that kind of looked like smallpox.
STEINHAUER: But this so-called cowpox was much milder.
GONZALEZ: And milkmaids who, you know, milked these cows, they sometimes got cowpox on their hands, and it was kind of an old wives' tale type thing, but people noticed that milkmaids who got cowpox wouldn't get smallpox. So this physician, Edward Jenner, he had the idea to take cowpox pus from a milkmaid, a human-to-human transfer.
STEINHAUER: So in 1796, he takes some cowpox pus from Sarah Nelmes, from her hand.
GONZALEZ: A milkmaid.
STEINHAUER: A milkmaid. And he scrapes it onto (laughter) an 8-year-old boy in the neighborhood named James Phipps.
GONZALEZ: He later exposes the kid to smallpox. And the kid didn't get smallpox, which was huge because you can't really die from cowpox. So Jenner publishes a paper.
STEINHAUER: And he coins the name Variolae vaccinae for the Latin word for cow, which is vacca.
GONZALEZ: So that's where we get vaccines from?
STEINHAUER: Yes. From cows.
GONZALEZ: They all mean cows?
STEINHAUER: (Laughter).
GONZALEZ: And almost 200 years after Jenner's vaccine, smallpox was eradicated.
Sarah Gonzalez, NPR News.
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