Vaccination has been one of the 20th Century's most effective tools for preventing disease and death. At the beginning of this century, five vaccines had been developed; in this century, 21 diseases have been added to the list of those that are preventable by vaccine.

At the end of the century, polio caused by wild virus has been eradicated from the Western Hemisphere; childhood vaccination levels in the United States are at an all-time high; and disease and death from diphtheria, pertussis, tetanus, measles, mumps, rubella and Haemophilus influenzae type b are at or near record lows. 

In 1900, 21,064 cases of smallpox were reported in the United States.; 894 of these persons died. The last case of smallpox in the United States was reported in 1949. The last case in the world was reported in 1977. The eradication of smallpox made it possible to stop efforts at prevention and treatment, including, in 1971, routine vaccination. One report, published in 1985, estimated that the U.S. recoups its investment in worldwide eradication of smallpox every 26 days. 

In the 1920's, other diseases that are now vaccine-preventable exacted an enormous toll. Cases of measles, diphtheria, and pertussis exceeded half a million per year; deaths from these diseases totaled about 20,000 annually. 

To fulfill the promise of vaccines in the future, the current vaccination delivery system must be strengthened, extended to new populations of adolescents and adults, and international efforts to deliver existing and new vaccines must be enhanced. 

Vaccine Facts.

The average annual number of smallpox cases in 1900-1904: 48,164. United States cases per year since 1950: 0. Worldwide cases per year since 1977: 0. 

The average annual number of diphtheria cases in the U.S. in 1920-1922 (the three years before vaccine development): 175,885. U.S. cases in 1998: 1.  

The average annual number of pertussis cases in 1922-1925 (the 4 years before vaccine development): 147,271. U.S. cases in 1998: 6,279.   

The estimated average annual number of tetanus cases in 1922-1926: 1,314. U.S. cases in 1998: 34.   

The average annual number of paralytic polio cases in 1951-1954 (the 4 years before vaccine licensure): 16,316. U.S. cases of wild type poliovirus in 1998: 0.   

The average annual number of measles cases in 1958-1962 (the 5 years before vaccine licensure): 503,282. U.S. cases in 1998: 89.   

The number of mumps cases in 1968 (the year reporting began and the first year after licensure): 152,209. U.S. cases in 1998: 606.   

The average annual number of rubella cases in 1966-1968 (the 3 years before vaccine licensure): 47,745. U.S. cases in 1998: 345.   

The estimated average annual number of cases of congenital rubella syndrome in 1966-1968 (the 3 years before vaccine licensure): 823. U.S. cases in 1998: 5.   

The estimated average annual number of Hib cases before vaccine licensure: 20,000. U.S. cases in 1998: 54.