Do you have a circular mark on your arm? This reveals a historical detail that few people know.

Many older people have a small, round, sunken scar on their left arm, which often goes unnoticed or is mistaken for a common birthmark. However, this birthmark has a long history and immense medical and social significance, representing one of the most important milestones in the global fight against disease.

This distinctive scar originated from the smallpox vaccine, one of the most widespread and effective vaccination campaigns in history. For several decades in the 20th century, millions of people worldwide were vaccinated to eradicate this infectious disease, which had caused countless deaths over the centuries. The vaccine, administered en masse in many countries until the late 1970s, left an indelible mark thanks to its method of administration.

Unlike modern vaccines, which are typically administered with a single-needle syringe, the smallpox vaccine was administered using a bifurcated needle designed to make multiple punctures in the same area of ​​skin, typically 10 to 15. This procedure caused a mild reaction in the area, which typically became inflamed and crusted. After healing, the area left a circular, depressed scar that, over time, became recognizable to an entire generation.