How to spot a cougar at the bar: the vaccine that left a scar

This story is from The Pulse, a weekly health and science podcast.

Subscribe on Apple Podcasts, Spotify or wherever you get your podcasts.

If you were a doctor practicing in the mid-19th Century, the look of this vaccine scar could tell you a lot.

If you’re 40 or older, you probably have a smallpox vaccine scar — depending on the country where you were born. Often it’s a dime-sized dent, usually on the upper left arm.

Back when smallpox was one of the most frightening and disfiguring diseases around, most kids in the United States got the vaccine, and ended up with a scar. But each year, fewer and fewer people have that mark.

Stephen Gluckman, who has been a physician for 45 years, is old enough to have the tell-tale scar. He’s an infectious disease doctor and director of Global Medicine at the Hospital of the University of Pennsylvania. Gluckman says most immunizations are delivered with an injection or pill. But to get the smallpox vaccine into the body — even the most modern technique–requires a bit of jabbing.

It’s called the puncture method. A health worker dips a small two-pronged needle into the vaccine solution, then taps it “vigorously” into the upper arm.

Sounds slightly barbaric, but that’s not really what causes the classic vaccine scar.

The vaccine is a live virus, a cousin of the virus that causes smallpox. That germ creates a small, local infection and nudges the body to mount its defenses. The virus starts multiplying, and within days, the immune system tries to push out the infection.

“It gets red and pussy and drains a little bit, and then it heals,” Gluckman said.

But different from a mosquito bite, the damage goes into deeper layers of skin. The blister crusts over, the scab falls off, and what’s left is a pockmark.

An example of a smallpox scar.

Reading the scars

If you were a doctor practicing in the mid-19th Century, the look of that vaccine scar could tell you a lot.

“You didn’t have blood tests to determine whether a person had immunities,” said Karie Youngdahl, director of the Web project the History of Vaccines at the College of Physicians of Philadelphia.

“The thought was if you had a big scar, that meant you had a good ‘take.’ What that means is — you had a robust local reaction to the vaccine,” Youngdahl said.

Doctors needed to distinguish a ‘good’ vaccine scar from an everyday acne mark or a leech bite. So around 1851, a French physician named J.E.B. Denarp Decanteleu categorized dozens of smallpox vaccines scars. Youngdahl found the doctor’s fragile and yellowing medical poster — a taxonomy of scars — in the college’s medical historical library.

Decanteleu created the poster after making a cast in stucco of different people’s vaccine scars. The poster includes beautiful illustrations of nasty-looking real-to-life sores.

Vaccine record on your arm

For hundreds of years, smallpox outbreaks cropped up around the world in nearly each new generation. They called it the ‘speckled monster.” When smallpox arrived in a city, it often killed a quarter to 30 percent of infected people.

Remember how we all worried about SARS and Ebola? Fears about smallpox were worse — and based less on scientific understanding. Quarantines separated families. Trade stopped and the economy was disrupted.

Historian Jennifer Keelan says a vaccine scar was a way to prove you weren’t a threat to your family and community.

“It was literally like wearing a vaccination record right on your arm,” Keelan said. “The more prominent the more clear—in some cases they thought the more discrete the scars there were–the better indication that you actually were protected from smallpox.”

Keelan writes about smallpox epidemics and teaches in the Department of Public Health at Concordia University of Edmonton in Alberta, Canada.

To stop smallpox, the United States and other countries inspected immigrants at the border.

Smallpox is highly contagious, but Keelan says it’s a somewhat apocryphal story often told over and over in the middle of a smallpox scare: “It always comes from away. They come in by train with a bit of a fever, and they land smack dab in the middle of your city, they infect thousands of people and then your entire city is overthrown by this epidemic.”

Countries also passed compulsory vaccine laws for citizens.

“Public health officials and local police would ask people to roll up their sleeves before they entered schools, before they entered factories, before they boarded trains or ships,” said Michael Willrich, a Brandeis University professor whose book is “Pox: An American History.”

“In tenement districts in American cities, vaccination squads would go through during epidemics and check people for vaccination scars, and if they didn’t have them, often vaccinated them against their will,” Willrich said.

But just like today, in the late 1800s there were vocal anti-vaccine lobbyists.

When a city was on high alert, Willrich says those opponents found ways to skip the vaccine and evade police.

“They’d put a little nitric acid on the spot where the vaccination would take place on the upper arm, a similar scar would form that could be used to kind of fake out the public health officials,” he said.

In the United States, the last natural case of smallpox was in 1949. And over the next decade, outbreaks slowed down in developing countries. That’s when the World Health Organization launched an ambitious global campaign to wipe out smallpox.

Community health workers in Africa, South America and Asia were trained to do mass vaccinations. Using a hypodermic injection gun — considered high-tech in the 1960s — workers could vaccinate as many as a thousand people an hour.

The College of Physicians has one stored away in its archives. The Ped-o-jet brand kind of looks like the hypospray gun Dr. McCoy used on Star Trek.

“The foot pedal when you pressed it down would deliver this burst of high pressure air, and travel through the gun then shoot out through the vaccine canister and penetrate the skin,” Youngdahl said.

The vaccine gun needed repairs all the time and turned out to be too intricate for fieldwork. So after a few years, health workers switched to the bifurcated needles still used today.

That new low-tech method was cheap and used a lot less vaccine, but Youngdahl suspects that patients briefly suffered a bit more.

“They’d do about 15 sharp little jabs. 1, 2, 3 up to 15,” she said.

The campaign worked. Smallpox was wiped out around the world and declared eradicated in 1980. Today, smallpox researchers and some people in the military are the only ones who routinely get the vaccine.

Hildegund Ertl, director of the vaccine center at The Wistar Institute in Philadelphia, was immunized against smallpox when she was a young researcher and graduate student in Germany.

“That was pretty awful, I was sick for two, three days,” she said. “My arm swelled up tremendously, I had a fever. I could barely move my arm; my lymph nodes were so swollen.”

Ertl says those side effects were relatively common and expected for the smallpox vaccine, that’s one reason the vaccine is typically administered in the left arm.

“Most people are right-handed. So, you don’t want to take away their ability to feed themselves, to write letters, to play with their computer–which we didn’t have at that time–that’s why we did the left arm,” Ertl said.

Once the smallpox threat was stamped out, Ertl says countries did the cost-benefit analysis for the vaccine, and between 1971 and 1972, the United States stopped offering the routine vaccine to children.

Millienials missed out, but earlier generations still have the battle scars of the war against smallpox.