Question

What type of immunity is due to the injection of an antigen?

Answer 1

Active immunity could be an answer but as you have used the word 'injection' so the most specific answer would be Artificially induced active immunity.

Explanation:

A type of active immunity that is achieved by introducing antigens in the body by artificial means is known as artificially acquired active immunity. Injecting vaccine is an example of this sort of immunity.

And if a person get exposed to antigens and person's body cells produce antibodies by their own then it would belong to naturally induced active immunity. In this case, antigens are not injected.

Hope it helps...