I can vividly remember observing a distinct mark on my mother’s arm during my childhood. It is situated up high, near her shoulder, resembling a ring of minor dents surrounding a larger indentation on her skin.

For some reason that caught my attention back then; the reason escapes me now. I only remember that it did, but as often happens, I eventually forgot about its existence in the years that followed.

In reality, I didn’t completely forget about it (it remains in the exact same spot, naturally), but I did overlook the fact that I was actually intrigued by its origin at one point in time. Maybe I inquired about it once, and my mother provided an explanation. If she did, though, I also forgot about that.

It wasn’t until one summer a few years ago when I assisted an elderly lady off a train, and I glimpsed the exact same mark in the exact same location as my mother’s scar. Needless to say, my curiosity was aroused, but with the train soon departing to my destination, I couldn’t directly inquire about the backstory of her scar.

Instead, I rang up my mother, and she disclosed that she had informed me on multiple occasions before – evidently my brain didn’t consider the response noteworthy enough to retain – and that her scar was a result of the renowned smallpox vaccine.

Smallpox is a viral, contagious ailment that once instilled fear in us humans. It triggers a notable skin rash and fever, and during the most severe outbreaks in the 20th century, claimed the lives of about 3 out of 10 victims according to the Centers for Disease Control and Prevention. Many other individuals were left scarred.

Thanks to a successful, widespread rollout of the smallpox vaccine, the virus was declared “eradicated” in the United States in 1952. In fact, by 1972, smallpox vaccinations were no longer part of routine immunizations.

However, up until the early ’70s, all children were inoculated against smallpox, and these vaccinations resulted in a very evident mark. Consider it as the original vaccine identification, if you will: a scar indicating that you had been effectively immunized against smallpox.

And indeed, you’ve guessed correctly, it’s that precise scar that my mother carries (as do nearly all others in her peer group).

What caused the smallpox vaccine to leave a mark?

The smallpox vaccine induced scars due to the body’s recuperative processes. The vaccine itself was administered quite differently from many contemporary vaccines, using a specialized double-pronged needle.

The individual administering the vaccine made multiple punctures in the skin (rather than the single injection typically given with today’s vaccines) to deliver the vaccine to the dermis of the skin (the layer below the epidermis).

The viral content within the vaccine then began to replicate, leading to the formation of round bumps. These bumps subsequently evolved into vesicles (small, fluid-filled blisters), which would eventually rupture and scab over with time.

The outcome is the notorious scar we have discussed in this piece.