Childhood Immunization Facts Immunization prevents disease . . .
Immunization is one of the most effective ways to prevent disease.
The level of vaccine-preventable disease has been reduced more than 99 percent since the introduction of vaccines. Prior to widespread immunization in the United States, infectious diseases killed or disabled thousands of children each year. Tens of thousands of cases of paralytic polio and an average of 450,000 measles cases were reported annually. A major cause of the measles epidemic was the failure to vaccinate children on time at 12 to 15 months of age. The World Health Organization declared the Americas free of polio in 1994.