The Real Reason Many People Have a Scar on Their Upper Left Arm
Smallpox, once a deadly and highly contagious virus, killed 3 in 10 infected people and left many survivors with permanent scars. Caused by the variola virus, the disease was eventually defeated through a groundbreaking vaccine made from a related virus, vaccinia. The vaccine, which triggered a strong immune response, left a distinct scar—usually a small,…
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