Smallpox was responsible for an estimated 300–500 million deaths during the 20th century alone.  In the early 1950s an estimated 50 million cases of smallpox occurred in the world each year. As recently as 1967, the World Health Organization estimated that 15 million people contracted the disease and that two million died in that year. After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in December 1979.  To this day, smallpox is the only human infectious disease to have been eradicated.