immunogen vs immunizing agent

immunogen and immunizing agent both are nouns.

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

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

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

immunogen (noun)	immunizing agent (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