As a child, I remember being fascinated by a noticeable scar on my mother’s arm. It rested high near her shoulder, a ring of tiny indentations circling a larger depression in her skin. For reasons I can’t quite explain, that scar caught my eye. At the time, I didn’t know what had caused it, and eventually, like so many childhood curiosities, I stopped thinking about it. It wasn’t that I forgot the scar existed—it was always there—but I did forget the curiosity I once felt about its origin.

Years later, an unexpected moment brought it all rushing back. One summer, I helped an elderly woman step off a train, and as she adjusted her sleeve, I noticed she had the exact same scar in the same place as my mother’s. My curiosity was instantly rekindled, but with the train about to depart, I couldn’t exactly stop her to ask about it. Instead, I called my mom to finally get the full story.

She reminded me—somewhat amused—that she had explained it before, though I clearly hadn’t retained the information. That scar, she said, was the result of her smallpox vaccination. Suddenly, it clicked. This was not just any scar, but one tied to a chapter of medical history that changed the world.

Smallpox was once one of the most feared illnesses in human history. A viral, contagious disease, it caused painful rashes, fever, and often left survivors permanently disfigured. According to the Centers for Disease Control and Prevention, during the most severe outbreaks of the 20th century, about three out of every ten people infected with smallpox died. The survival rate was higher than many other plagues, but the scars—both physical and emotional—were devastating for entire communities.

Thanks to widespread vaccination efforts, smallpox was eradicated in the United States by 1952. By 1972, the vaccine was no longer part of routine childhood immunizations. But for decades leading up to that, every child was vaccinated, and nearly all of them carried the same telltale scar. In many ways, that little mark was like an early form of a vaccine passport, proof that you were protected from one of humanity’s deadliest diseases.

What makes the smallpox vaccine unique is how it was administered. Unlike today’s vaccines, which are typically delivered with a single injection, the smallpox vaccine used a specialized two-pronged needle. The person administering the shot would make multiple tiny punctures in the skin, transferring the vaccine to the dermis, the layer just beneath the surface.

The body’s response was intense but intentional. Those punctures produced small raised bumps that soon transformed into vesicles—tiny fluid-filled blisters. These would eventually burst and scab over before healing. Once the skin closed, the lasting imprint was left behind: a distinctive round scar that many people of a certain generation still carry today.

Seeing that scar on both my mother and the elderly woman reminded me that medicine is not just about science—it’s also about memory. Each scar told a story, one that connected generations who lived through a time when smallpox was still a genuine threat. My mother’s arm, in a way, carried proof of victory over a disease that once claimed millions of lives.

Today, smallpox is considered eradicated worldwide, thanks to one of the most successful vaccination campaigns in history. Yet the scars remain, quiet reminders etched into skin, linking those who lived through that era. It’s a strange thought: some of the most unassuming marks on our bodies are actually monuments to medical progress.

So, if you’re old enough to bear that smallpox vaccination scar, know that it isn’t just a mark. It’s a testament to resilience, science, and survival—a visible reminder that humanity fought back against one of its greatest threats and won.