Many people remember noticing a small, round scar on the upper arm of a parent or grandparent without ever knowing its origin. That distinctive mark, often shaped like a circle of tiny indents around a larger one, comes from the smallpox vaccine, which was routinely given to children until the early 1970s. Smallpox was once one of the world’s most feared diseases, causing severe illness, disfigurement, and death in millions of people. Through a massive global vaccination effort, the disease was eventually eliminated in many countries, with routine vaccinations in the United States ending in 1972 once the threat had largely disappeared.

The scar itself formed because the vaccine was administered differently from most modern shots. Instead of a single injection, doctors used a special two-pronged needle to make multiple tiny punctures in the skin, allowing the vaccine virus to trigger an immune response. This process produced a small blister that later scabbed and healed, leaving behind the permanent mark many older adults still carry today. Far from being just a curious blemish, the scar became a visible sign that a person had been vaccinated and protected against a deadly disease. For many families, it now serves as a quiet reminder of a time when vaccination campaigns helped defeat one of humanity’s most dangerous infections.