Many people of a certain age have a small, round, sunken scar on their upper left arm that often goes unnoticed or is mistaken for a simple birthmark.
However, this mark on the skin carries a story of great medical and social importance and represents one of the most significant milestones in the global fight against disease.
That distinctive scar comes from the smallpox vaccine, one of the most widespread and successful immunization campaigns in history. For several decades during the 20th century, millions of people around the world were vaccinated in an effort to eradicate this infectious disease, which had caused countless deaths over the centuries. The vaccine, administered on a massive scale until the late 1970s in many countries, left an unmistakable mark because of the way it was given.
A Very Different Vaccination Method
Unlike modern vaccines, which are usually administered with a single-needle syringe, the smallpox vaccine was delivered using a bifurcated needle designed to make multiple punctures in the same area of skin, typically between 10 and 15. This procedure caused a mild reaction in the area, which would swell and form a scab. Once healed, it left behind a circular, indented scar that over time became a recognizable feature for an entire generation.
When and Why Vaccination Stopped
The widespread use of this vaccine was discontinued between 1972 and 1980, when the World Health Organization (WHO) officially declared smallpox eradicated. Thanks to that historic decision, the virus that caused the disease has completely disappeared from nature. Since then, the vaccine has only been used in very specific cases, such as for certain laboratory workers or military personnel who might be exposed to manipulated versions of the virus.
Smallpox Scar vs. BCG Scar
One common question is whether this scar can be confused with the mark left by the BCG vaccine, which is used against tuberculosis. Although both leave marks on the skin, there are clear differences: the BCG scar is usually more raised and is sometimes located on the right arm, while the smallpox scar is deeper, circular, and generally found on the left arm.
Possible Ongoing Medical Relevance
Beyond its value as a historical symbol, this mark may still have medical relevance. Some recent studies suggest that people who received the smallpox vaccine in childhood might retain a degree of cross-immunity against related viruses, such as the one that causes monkeypox. While this hypothesis is still being evaluated, it reinforces the importance of vaccination campaigns and their long-term impact.
A Living Reminder of Medical History
Carrying this scar is, in a way, like wearing a testimony on the skin of a crucial moment in medical history. It is a visible reminder of how science, through collective effort, managed to contain and eliminate one of the most devastating diseases humanity has ever known.
So if you notice this mark on your arm or on that of an older family member, you now know that it is not just a scar, but evidence that they were part of a generation that unknowingly contributed to one of the greatest public health achievements of all time.
