Vaccines can be constituted of dead agents of disease, of inactivated agents of disease, of inactivated toxins or of fragments of the infectious agent. Examples of some vaccines and their type of antigenic agents are: BCG, inactivated tuberculosis bacilli; antitetanic vaccine, inactivated toxin; antidiphtheric, inactivated toxin; antipolio Salk, dead poliovirus; antipolio Sabin, attenuated (inactivated) poliovirus.