Which disease was targeted by mass vaccination campaigns in the early 20th century?

Mass vaccination campaigns in the early 20th century primarily targeted smallpox due to its devastating impact on populations. Smallpox was a highly contagious and deadly disease that caused severe illness and disfigurement. The widespread use of the smallpox vaccine, which Edward Jenner had developed at the end of the 18th century, began to gain significant traction in the early 1900s.

Governments and health organizations recognized the effectiveness of vaccination in preventing smallpox outbreaks, leading to nationwide campaigns aimed at immunizing large segments of the population. These programs were pivotal in the eventual global eradication of the disease in 1980, as confirmed by the World Health Organization.

The other diseases listed, while important in public health measures, did not experience mass vaccination campaigns to the same degree during the early 20th century. For example, vaccinations against polio gained momentum later in the mid-20th century, while measles and tuberculosis vaccine programs became more established from the 1950s onwards.