Vaccine seems like the wrong term as I think of it as preventative. Perhaps there is no precise term for a treatment that uses the immune system to fight an existing disease in the body
There are two types of vaccines: prophylactic (to prevent or ameliorate the effects of a future infection by a pathogen) and therapeutic (to fight a disease that has already occurred, such as cancer).
Rabies vaccine is also given after infection.
That is post-exposure antibodies which kill the virus, plus the vaccine.
Tetanus can be too
Perhaps there is no precise term for a treatment that uses the immune system to fight an existing disease in the body
Immunotherapy?
Regardless, vaccine is indeed the word used in the field. You should just update your definition.