As a child, I was strangely fascinated by a scar on my mother’s upper arm. It looked like a circle of tiny indentations surrounding a larger mark, sitting high near her shoulder. For years I forgot about it, until one summer afternoon when I helped an elderly woman off a train and noticed the exact same scar in the exact same spot. Curious, I called my mother, and she reminded me that she had explained it many times before. The scar came from the smallpox vaccine, a vaccination once routinely given to children before the early 1970s. Smallpox was a deadly viral disease that caused severe rashes, fever, and often death or disfigurement. During major outbreaks in the twentieth century, millions of people suffered from the disease. Thanks to widespread vaccination campaigns, smallpox was declared eradicated in the United States in 1952, and routine vaccinations eventually stopped in 1972. For many people of my mother’s generation, however, the vaccine left behind a permanent and recognizable scar that became proof they had been protected from one of history’s most dangerous diseases.

The smallpox vaccine created scars because it was administered very differently from modern vaccines. Instead of a single injection, doctors used a special two-pronged needle to make multiple punctures in the skin. The vaccine virus then multiplied in the dermis, causing bumps and fluid-filled blisters to form before eventually scabbing over. As the skin healed, it left behind the familiar circular scar that many older adults still carry today. Unlike most modern vaccinations, which leave little or no visible trace, the smallpox vaccine produced a mark that lasted a lifetime. Seeing that scar on both my mother and the elderly woman made me realize how many people quietly share a connection to an important moment in medical history. What once seemed like an ordinary blemish on my mother’s arm suddenly became a reminder of a disease humanity fought hard to eliminate and the generations protected because of it.