A smallpox vaccine scar is a distinctive mark that smallpox vaccination leaves behind. The scar may be round or oblong, and it may appear deeper than the surrounding skin. Usually, the scar is smaller than the diameter of a pencil eraser, though it can be larger.

What immunization shot leaves a scar?

The smallpox vaccine holds a live virus. It creates a controlled infection that forces your immune system to defend your body against the virus. The exposure to the virus tends to leave a sore and itchy bump behind. This bump later becomes a larger blister that leaves a permanent scar as it dries up.

Does BCG vaccine always leave a scar?

It's normal for it to leave a small scar. Occasionally, there may be a more severe skin reaction, but this should heal within several weeks. If you're worried that your or your child's skin reaction is abnormal or that the spot may have become infected, contact a GP.