Smallpox, one of history’s most devastating viral infections, caused severe fever and an unmistakable skin rash. By the early 20th century, smallpox outbreaks wreaked havoc,

with the virus claiming the lives of 3 out of every 10 infected individuals. Survivors often bore lifelong reminders of their struggle, with scars frequently etched into their faces.

The variola virus was responsible for this highly contagious and deadly disease. In response, scientists developed a groundbreaking vaccine using a live virus called vaccinia, closely related to variola but not capable of causing smallpox. The vaccine spurred the immune system to produce antibodies capable of fighting off smallpox.

Thanks to this medical breakthrough, smallpox was declared eradicated in the early 1950s, a feat so monumental that routine vaccinations in the United States ceased in 1972. Today, only those working in high-risk environments, such as labs handling the virus, receive the vaccine.