Why do so many people have a small scar on their left arm?

If you've noticed a small, round scar on someone's left arm—or if you have one yourself—know that it's a mark left by a historic vaccine. This scar is a legacy of vaccination campaigns against smallpox, a devastating disease that plagued humanity for centuries.
The smallpox vaccine: a turning point in medical history.

Smallpox, an extremely contagious and often fatal viral disease, ravaged entire populations until the invention of the vaccine in 1796 by Edward Jenner. This vaccine, developed from the vaccinia virus (an attenuated form of smallpox), was the first in history and significantly reduced epidemics. In 1952, smallpox was declared eradicated in the United States, and by 1980, it had been completely eradicated worldwide, which remains a major medical achievement.

Why is this scar so unusual?

scar

Unlike modern vaccines, the smallpox vaccine was administered using a unique technique involving a bifurcated needle. This needle, equipped with two small points, pierced the skin repeatedly to introduce a small amount of the virus into the dermis. This method created a characteristic skin reaction: a blister formed at the injection site, which eventually burst, leaving behind a scab and then a circular scar. "This scar is a testament to an era when medicine fought against otherwise deadly diseases," explains Lydia Mammar, a specialist in medical history.

Why on the left arm?

För fullständiga tillagningssteg, gå till nästa sida eller klicka på Öppna-knappen (>), och glöm inte att DELA med dina Facebook-vänner.