Immunization as a noun is the process by which an individual is exposed to a material that is designed to prime his or her immune system against that material. while Immunisation as a noun is the process of immunising signalling and traction power supplies so they don't interfere with each other.
Part of speech: noun
Definition: The process by which an individual is exposed to a material that is designed to prime his or her immune system against that material. One such exposure.
Part of speech: noun
Definition: The process of immunising signalling and traction power supplies so they don't interfere with each other.
We hope you now know whether to use Immunization or Immunisation in your sentence.