Many people have a small, round scar on their upper arm from the smallpox vaccine, which was common before the 1970s. The vaccine used the live Vaccinia virus to help the body build immunity against the smallpox-causing Variola virus.
After receiving the shot, blisters form at the injection site, eventually healing into a circular scar. The process is a result of the vaccine causing temporary swelling, followed by a lump that develops into a tumor and eventually turns into an ulcer.
Around 6 to 8 weeks after the vaccination, the blister opens, oozes fluid, and heals into a permanent scar. This sequence is a sign of the body’s immune response to the virus.
Smallpox was largely eradicated by the early 1970s, and vaccinations stopped in the 1980s. The scar remains as a reminder of the fight against this once-deadly disease.
