Definition from Wiktionary, the free dictionary
Alternative forms 
- immunisation (UK)
- (US, uncountable) The process by which an individual is exposed to a material that is designed to prime his or her immune system against that material.
- Immunization against influenza is important for all child-care workers.
- (US, countable) One such exposure.
- The first immunization a baby gets is against HBV.
Derived terms 
process of immunization