Unlike many modern vaccines, the smallpox vaccine was delivered using a special bifurcated needle that repeatedly pricked the skin, introducing the virus into the upper layers. This method triggered a localized infection that formed a blister, then a scab, and eventually healed into the distinctive scar still visible decades later. The scar became a badge of protection—evidence that the immune system had successfully learned how to defeat a deadly enemy.
The results of widespread vaccination were extraordinary. As immunization campaigns expanded globally, smallpox cases plummeted. By the early 1950s, the disease was declared eradicated in many parts of the world, and in 1980 the World Health Organization officially announced that smallpox had been eliminated worldwide—the first human disease ever to be completely eradicated. In the United States, routine smallpox vaccinations ended in 1972, as the risk of infection had effectively vanished.
Today, smallpox exists only in tightly secured laboratory samples, and vaccination is limited to a small group of people who work in high-risk environments, such as researchers handling the virus or certain military personnel. For everyone else, that small scar on the upper left arm remains a visible reminder of a time when a simple vaccination helped save millions of lives—and changed the course of human history.