A lot times they're local, at the site of the immunization, where it was given.
The most promising of these is that of Todd , produced by the immunization of suitable animals.
When I took office, immunization levels for preventable childhood diseases had fallen to 70%.
Note: Frequently, schoolchildren are required by state law to be immunized against certain diseases. Because of such widespread immunization, many diseases that used to be fairly common, including smallpox, tetanus, and whooping cough, have become rare.