| Feature | BCG Scar (Tuberculosis) | Smallpox Scar |
|---|---|---|
| Size | Smaller (about 5-8mm) | Larger (about 10-15mm) |
| Appearance | Usually round, slightly indented | Often more textured, may have a "dimpled" center |
| Timing | Given in infancy (in many countries) | Given later in childhood (in countries that used it) |
| Current use | Still used in many countries | Discontinued worldwide after 1980 |
Smallpox vaccination ended globally in 1980 after the disease was declared eradicated. If you were born after 1980, your scar is almost certainly from BCG.
If you're older and have a larger, more textured scar, it might be from smallpox. But for most people reading this, it's BCG.
Misconception #3: "It's from a bad reaction to a regular shot."
The truth: The BCG vaccine is unique in how it's given.
Most vaccines are injected into muscle (intramuscular) or just under the skin (subcutaneous). These methods are designed to minimize tissue reaction and scarring.
BCG is different. It's injected into the skin itself (intradermal), creating a small wheal (a raised bump). Over the next few weeks, that bump becomes a pustule, then ulcers, then finally heals into a scar.
This reaction is intentional. It's a sign that the immune system has responded to the vaccine. A BCG shot that doesn't leave a scar may not have been effective.
That scar isn't a complication. It's proof that the vaccine worked.
Misconception #4: "I must have injured myself as a child and forgotten."
The truth: This is a common explanation people invent when they don't know about the vaccine.
It makes sense—most childhood injuries leave some mark, and we forget many of them. But the BCG scar has a distinctive appearance and location that sets it apart:
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Location: Always on the left or right upper arm (deltoid area)
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Appearance: Round, uniform, slightly depressed
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Consistency: Nearly identical in size and shape across millions of people
If you have a scar that matches this description, it's almost certainly from BCG vaccination—not a fall, a burn, or a scrape you've forgotten.
Misconception #5: "It's a brand or tribal mark."
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