I have a clear memory of noticing a distinct scar on my mother’s arm when I was a child. It sits high up, close to her shoulder, taking the appearance of what looks like a ring of small indents in her skin around a larger indent.

Don’t ask me why that specifically attracted my attention all those years ago; I don’t remember. I recall only that it did, but as is so often the case, I sort of forgot it existed over the following years.

Well, obviously I didn’t forget it existed (it’s still in the same place it always was, of course), but I did forget that at one point in time I was fascinated with what had caused it. Perhaps I asked my mother once and she explained. If she did, though, I forgot that as well.

Instead I called my mother, and she revealed that she in fact told me more than once – obviously my brain didn’t deem the answer important enough information to retain – and that her scar had come courtesy of the famous smallpox vaccine.

Smallpox is a viral, infectious disease that once terrorized us humans. It causes a significant skin rash and fever, and during the most rampant outbreaks in the 20th century, killed an estimated 3 out of 10 victims according to the Centers for Disease Control and Prevention. Many other sufferers were left disfigured.