provides reliable protection.
If you are under 45, it is far more likely that a round scar on your arm comes from the BCG vaccine (for tuberculosis)—which is routinely administered at birth in many countries outside the United States—rather than from the smallpox vaccine. The two can easily be confused, as they can leave similar-looking scars.
Why did the vaccine leave a scar in the first place? Most modern vaccine administrations—specifically the clinical injection method—are performed using a bifurcated (two-pronged) needle that has been dipped into a vaccine solution.
