This process usually follows several stages:
A small bump appears at the injection site.
The bump may develop into a tiny blister.
A small ulcer sometimes forms.
The area gradually heals over several weeks.
A permanent circular scar remains.
This sequence is considered a normal part of the healing process.
Not everyone develops exactly the same scar. Some people have a tiny, barely visible mark, while others have a larger, more noticeable indentation.
The size depends on factors such as individual healing, immune response, and the injection technique used.
Why Was It Usually Given on the Upper Arm?
The upper arm became the preferred injection site for several practical reasons.
It provides easy access for healthcare workers, heals well, and leaves a scar in an area that generally causes little cosmetic concern.
This location also allows medical professionals to verify that the vaccine was successfully administered, since the scar often serves as visible evidence of prior vaccination.
Is the Scar Dangerous?
For healthy individuals, the scar itself is completely harmless.
It does not indicate an active infection or illness.
It is simply healed skin where the immune system responded to the vaccine.
The scar generally requires no treatment and causes no long-term health problems.
Only in very rare situations—typically involving people with severely weakened immune systems—can complications occur after BCG vaccination.
For the vast majority of people, however, the scar remains nothing more than a lifelong reminder of childhood immunization.
Why Don’t Younger People Have the Scar?
One reason many younger adults have never seen this scar is that vaccination policies have changed in many countries.
As tuberculosis became less common in regions with strong healthcare systems, routine universal BCG vaccination was gradually discontinued.
Instead of vaccinating every newborn, many countries now recommend the vaccine only for individuals considered at higher risk of exposure.
As a result, people born in recent decades may never have received the vaccine at all.
Tuberculosis: A Disease That Changed History
To understand why so many people received the BCG vaccine, it helps to appreciate just how devastating tuberculosis once was.
For centuries, TB claimed millions of lives worldwide.
