As a child, I was fascinated by a distinctive scar on my mother’s upper arm. Located near her shoulder, it looked like a circle of small indentations surrounding a larger mark. For reasons I can’t fully explain, it caught my attention and sparked my curiosity. Over time, however, I stopped thinking about it and eventually forgot that I had ever wondered about its origin.

Years later, while helping an elderly woman off a train, I noticed she had an almost identical scar in the exact same location. The sight immediately reminded me of my mother’s mark and reignited my curiosity. Since I didn’t have time to ask the woman about it, I called my mother instead. She explained that the scar was the result of a smallpox vaccination and reminded me that she had told me the same thing years earlier.

Smallpox was once one of the most feared infectious diseases in the world. The virus caused severe fever, a widespread rash, and often death or permanent disfigurement. Thanks to a highly successful vaccination campaign, smallpox was eliminated in the United States by the early 1950s, and routine vaccinations against the disease ended in the early 1970s.

The vaccine was administered differently from most modern vaccines. A special two-pronged needle made multiple punctures in the skin, allowing the vaccine virus to trigger a localized reaction. Small blisters formed, eventually scabbing over and healing. This process often left behind the recognizable scar that many older adults still carry today.