Here’s the full story:
💉 The Smallpox Vaccine Scar
The round scar is most commonly from the Smallpox vaccine.
Why it leaves a scar:
The original vaccine didn’t use a typical injection.
Doctors used a bifurcated needle to prick the skin multiple times with a live vaccinia virus (a related but safer virus).
This caused:
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A raised bump
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Then a blister
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Then a scab
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Finally → a small, round scar
The scar forms because the vaccine created a localized skin infection that triggered a strong immune response.
🕰️ Why Younger People Usually Don’t Have It
Routine smallpox vaccination stopped in many countries after the disease was eradicated.
In fact, the World Health Organization declared smallpox eradicated in 1980 — one of the greatest achievements in public health.
So:
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People born before the early 1980s often have the scar.
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Those born after usually don’t.
🌍 Why It Was So Important
Before eradication, Smallpox was:
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Highly contagious
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Often deadly
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Responsible for millions of deaths globally
The vaccine campaign eliminated it worldwide.
🔎 Could It Be Something Else?
Less common causes of similar scars:
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BCG vaccine (for tuberculosis)
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Old skin infections
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Childhood injuries
But a perfectly round scar on the upper upper arm in someone over ~40 years old is most likely smallpox vaccination.
🧠 Interesting Fact
The original smallpox vaccine was developed by Edward Jenner in 1796, making it the first successful vaccine in history.
If you’d like, tell me:
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Roughly how old is the person with the scar?
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Which country they grew up in?
That can help narrow down the most likely cause.