During the 20th century, substantial achievements have been made in the control of many vaccine-preventable diseases. Information about disease and death during the 20th century was obtained from the Morbidity and Mortality Weekly Report annual summaries of notifiable diseases and reports by the US Department of Health, Education, and Welfare. For smallpox, routine vaccination was ended in 1971. Overall, American vaccination coverage is at record high levels. Coverage for rotavirus vaccine, licensed in December 1998, has not yet been measured among children aged 19 to 35 months.
Smallpox is the only disease that has been eradicated.
The pattern in the decline of smallpox was sporadic. Outbreaks of variola major occurred periodically in the first quarter of the 1900s and then ceased abruptly in 1929. Outbreaks of variola minor declined in the 1940s, and the last case in the United States was reported in 1949. The eradication of smallpox in 1977 enabled the discontinuation of prevention and treatment efforts, including routine vaccination. Polio vaccine was licensed in the United States in 1955.