- a substance composed of dead or weakened bacteria (or other pathogens), or their toxins, that induces immunity when introduced into a body
Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby
- A preparation of dead or weakened pathogen, or of derived antigenic determinants, that is used to induce formation of antibodies or immunity against the pathogen.