immunizing agent vs immunogen

immunizing agent and immunogen both are nouns.

Word	Noun	Adjective	Verb	Adverb
immunizing agent	Yes	No	No	No
immunogen	Yes	No	No	No

As nouns, immunizing agent and immunogen are synonyms defined as:

immunizing agent and immunogen: any substance or organism that provokes an immune response (produces immunity) when introduced into the body

immunizing agent (noun)	immunogen (noun)
any substance or organism that provokes an immune response (produces immunity) when introduced into the body	any substance or organism that provokes an immune response (produces immunity) when introduced into the body