Toxoids are inactivated toxic compounds from micro-organisms
in cases where these(rather than the micro-organism itself) cause illness, used prior to an encounter with the toxin of the micro-organism.
Diphtheria Toxoid is not given as a single injection,
but rather is combined with tetanus Toxoid and, often, pertussis vaccine in a preparation called Tdap, DTaP, Td, or DT.