The United States records 206,000 cases of diphtheria in 1921, resulting in 15,520 deaths. Diphtheria death rates range from about 20% for those under age five and over age 40, to 5%-10% for those aged 5-40.

After becoming one of the country's leading causes of death, diphtheria infection rates will drop significantly after the introduction of the vaccine in the mid-1920s, and then again when antibiotics become available to treat the disease.