Smallpox was once one of the most dangerous and contagious diseases in human history. It was caused by the variola virus and spread easily from person to person through airborne droplets or contact with contaminated items. The disease had a very high mortality rate, killing approximately 3 out of every 10 people who became infected. Those who survived were often left with permanent scars, especially on the face and body, and in some cases, even blindness.

The breakthrough in fighting smallpox came through vaccination. Scientists developed a vaccine using a related virus called vaccinia, which is similar enough to the variola virus to trigger a strong immune response but not cause the disease itself. This vaccine played a crucial role in the global effort to eliminate smallpox.

When people received the smallpox vaccine, it was administered using a special two-pronged (bifurcated) needle. This tool was used to puncture the skin multiple times in a small circular area, typically on the upper left arm. The process caused a localized reaction, which led to the formation of a scab, and later, a small round scar. That scar became a visible and lasting reminder of the vaccination.

The global vaccination campaign was so successful that smallpox was officially declared eradicated in 1980 by the World Health Organization. Because of this achievement, routine smallpox vaccinations in the United States stopped in 1972. Today, only individuals who are considered at high risk—such as laboratory workers handling the virus or certain military personnel—are still vaccinated against smallpox.

Although most people experienced only mild side effects from the vaccine, some rare but serious complications did occur, which is another reason routine vaccinations were stopped once the disease was no longer a threat.

Today, the small round scar left behind by the vaccine has become increasingly rare, especially among younger generations who were never vaccinated. For older generations, however, the scar serves as a powerful symbol of one of medicine’s greatest achievements: the complete eradication of a deadly disease through science, cooperation, and the power of vaccines.