If you’re in your forties, fifties, or sixties, you might have noticed a small round scar on your upper arm. Have you ever wondered where it came from? Well, chances are it’s a leftover mark from the smallpox vaccine you received many years ago.

Before the 1970s, the smallpox vaccine was quite common. It was designed to protect people from the deadly smallpox virus. The vaccine used live Vaccinia virus to stimulate the immune system and create a defense against Variola, the virus responsible for smallpox.

So, what actually happened after you received the vaccination? Well, blisters formed at the injection site. These blisters then crusted over and eventually healed within a couple of weeks. The scars we see today are the result of this healing process.

Each needle puncture during the vaccination delivered a small dose of the vaccine, causing blisters to form. As the injection site expanded slightly, the blisters appeared and eventually healed, leaving behind the circular scar.

But that’s not all. About 6 to 8 weeks after the vaccination, a lump similar to a mosquito bite would develop. This lump would later open, exuding fluid, and eventually transform into an ulcer. Finally, it would heal, leaving behind an indelible scar.

It’s important to note that smallpox has been eradicated in most parts of the Western world. The vaccine played a crucial role in achieving this milestone. Since the Variola virus is no longer a threat, immunizations against smallpox were discontinued in the 1980s.

So, next time you notice that scar on your upper left arm, remember that it’s not just a mark on your skin. It’s a historical record of a once-dangerous disease and a reminder of the protection you received against smallpox.