As a child, I noticed a peculiar scar on my mother’s upper arm — “a ring of small indents surrounding a larger one.” Years later, I saw the same scar on an elderly woman and asked my mother about it. She said it was from the smallpox vaccine.

Smallpox was a deadly disease caused by the variola virus, killing about 30% of those infected and leaving survivors scarred. “For centuries, it devastated populations around the world.” Global vaccination campaigns eventually eradicated it, and the World Health Organization declared smallpox gone in 1980. Routine vaccinations in the U.S. had stopped in 1972.

The vaccine was unusual. It used “a bifurcated needle, a small two-pronged instrument dipped into the vaccine solution.” The skin was pricked several times, introducing a live virus called vaccinia, related to smallpox but far less dangerous. A blister formed, scabbed, and healed, leaving the circular scar recognized worldwide.

For many, the scar was more than a mark — it was “a visible reminder that they were immunized against one of history’s deadliest diseases.” Today, few under 50 have it, since smallpox vaccination is no longer needed.

The eradication of smallpox remains one of humanity’s greatest medical victories. Those who still bear the scar carry “a living piece of history—proof of science’s triumph over a once-unstoppable killer.”