immunogen vs vaccinum

immunogen and vaccinum both are nouns.

Word	Noun	Adjective	Verb	Adverb
immunogen	Yes	No	No	No
vaccinum	Yes	No	No	No

As nouns, vaccinum is a hyponym of immunogen; that is, vaccinum is a word with a more specific, narrower meaning than immunogen:

immunogen: any substance or organism that provokes an immune response (produces immunity) when introduced into the body
vaccinum: immunogen consisting of a suspension of weakened or dead pathogenic cells injected in order to stimulate the production of antibodies

Other hyponyms of immunogen include vaccine, toxin antitoxin.

immunogen (noun)	vaccinum (noun)
any substance or organism that provokes an immune response (produces immunity) when introduced into the body	immunogen consisting of a suspension of weakened or dead pathogenic cells injected in order to stimulate the production of antibodies