I have a vivid memory from childhood of noticing a distinct scar on my mother’s arm. It’s located high on her shoulder, appearing as a ring of small indentations encircling a larger, deeper mark.
I can’t recall why this scar caught my attention back then—it just did. Like so many childhood curiosities, though, it eventually faded from my mind.
Of course, I didn’t completely forget its existence (it’s still exactly where it has always been), but I did forget how intrigued I once was by its origin. Perhaps I asked my mother about it at some point, and maybe she explained. If she did, the details slipped away over time.
That changed one summer a few years ago when I helped an elderly woman off a train. As she moved past me, I caught sight of the same type of scar in the exact spot as my mother’s. My curiosity was reignited, but with the train about to depart, I didn’t have the chance to ask her about it.
Later, I called my mother and asked her again. She reminded me—apparently not for the first time—that her scar was the result of the smallpox vaccine.
Smallpox: A Deadly Disease of the Past
Smallpox was a highly contagious viral disease that plagued humanity for centuries. It caused severe fever and a widespread skin rash. According to the Centers for Disease Control and Prevention (CDC), during the worst outbreaks in the 20th century, smallpox killed around 3 out of every 10 infected individuals. Many survivors were left with permanent scarring or disfigurement.
Thanks to a massive global vaccination campaign, smallpox was declared eradicated in the United States in 1952. By 1972, routine smallpox vaccinations were discontinued. However, up until the early 1970s, children were universally vaccinated against the disease, and the vaccine left behind a distinctive mark—a scar that served as a visible indicator of immunity.
In a way, this scar was an early version of a “vaccine passport,” signaling that an individual was protected from a devastating disease.
And yes, it’s this very scar that my mother—and nearly everyone of her generation—bears.
Why Did the Smallpox Vaccine Leave a Scar?
The scar from the smallpox vaccine was a natural result of how the vaccine was administered and how the body healed afterward. Unlike modern vaccines, which are typically delivered with a single injection, the smallpox vaccine used a specialized bifurcated (two-pronged) needle.
The person administering the vaccine made multiple punctures in the skin to deposit the vaccine into the dermis, the layer of skin beneath the epidermis. The vaccine contained a live virus that triggered a localized immune response, causing the formation of raised bumps at the injection site.
Over time, these bumps developed into fluid-filled blisters (vesicles), which eventually burst and scabbed over. When the scabs fell off, they left behind the well-known smallpox vaccine scar.
This iconic mark is more than just a relic of a medical procedure—it’s a lasting testament to one of humanity’s greatest triumphs in eradicating a deadly disease.
