Smallpox was a highly contagious disease caused by the variola virus. It typically began with symptoms including high fever and severe fatigue before producing its characteristic rash. The lesions eventually filled with fluid and pus before crusting over, and survivors could be left with extensive scarring.
Vaccination became one of the most important tools for eliminating the disease.
The traditional smallpox vaccine contained vaccinia virus, a virus related to the one that causes smallpox but not the variola virus itself. The vaccine therefore could not give someone smallpox.
Unlike many familiar vaccines administered with a conventional injection, smallpox vaccination was commonly performed on the upper arm using a bifurcated needle.
A successful vaccination produced a distinctive local reaction. Within several days, a red, itchy lesion developed. It then became a blister, later formed a scab, and eventually healed. When the scab fell off, it frequently left behind a small permanent scar.
That’s why so many people from certain generations have similar-looking marks in approximately the same place.
Why Routine Smallpox Vaccination Disappeared
The scar also represents one of medicine’s greatest public-health successes.
In 1967, the World Health Organization intensified the international effort to eradicate smallpox through vaccination, surveillance and rapid containment of outbreaks.
The last naturally occurring case was recorded in Somalia in 1977. After extensive surveillance found no continuing natural transmission, the World Health Assembly officially declared smallpox eradicated in 1980.
In the United States, routine smallpox vaccination had already ended in 1972, after the disease had been eliminated nationally and the risk no longer justified routinely vaccinating the general population.
Today, routine smallpox vaccination is not recommended for the general U.S. public, although vaccination is still used for certain people whose occupations put them at risk of exposure to orthopoxviruses.
But It Could Also Be a BCG Scar
This distinction matters, especially outside the United States.
The BCG vaccine is used to protect children against serious forms of tuberculosis and has been widely administered in many countries. The CDC notes that many people born outside the United States have received it, while BCG is not generally used routinely in the U.S.
So seeing a circular scar on someone’s upper arm doesn’t automatically tell you which vaccine they received.
Age, country of birth and vaccination history can provide much better clues.
A Tiny Mark From a Very Different Era
For someone who really does carry a smallpox vaccination scar, that little mark has an extraordinary history behind it.
Smallpox was once one of humanity’s most devastating infectious diseases. WHO estimates that it killed hundreds of millions of people during the 20th century alone.
Today, it no longer circulates naturally anywhere in the world.
So that small scar on an older person’s arm may be more than an old vaccination mark. It can be a physical reminder of the enormous international effort that ultimately eliminated a disease that had threatened humans for thousands of years.
And if you’ve always wondered what your own circular arm scar came from, don’t rely on its appearance alone. Ask relatives, look for old vaccination records if they’re available, or discuss it with a healthcare professional.
Sometimes the smallest marks carry surprisingly large pieces of history.