When I was little, I used to notice a small, round scar high up on my mother’s arm — almost like a tiny ring of dots pressed into her skin. It fascinated me, though I never quite remembered to ask where it came from.

Years later, while helping an elderly woman off a train one summer, I saw the same mark in the same spot. That’s when my curiosity returned, and I finally asked my mother about it. Her answer surprised me: it was from the smallpox vaccine.

A Tiny Scar with a Big Story

Before modern vaccines became what they are today, smallpox was one of the most feared diseases in the world. It caused fever, rashes, and left many survivors with permanent scars. According to the CDC, the virus once killed about 3 out of every 10 people who caught it — until the smallpox vaccine changed everything.

Thanks to a massive global vaccination effort, smallpox was officially declared eradicated in the early 1980s — one of humanity’s greatest medical achievements. By 1972, routine smallpox vaccinations had stopped in the U.S., meaning only people born before that time typically have the signature scar.

Why Did the Vaccine Leave a Mark?

Unlike most modern shots, the smallpox vaccine was given using a special two-pronged needle. Instead of one quick injection, it required several tiny punctures in the same spot.

After vaccination, a small bump would form, then turn into a blister, scab, and finally heal — leaving behind that distinctive round scar many people still carry today.