: a toxin of a pathogenic organism treated so as to destroy its toxicity but leave it capable of inducing the formation of antibodies on injection <diphtheria toxoid>—called also anatoxin
Bacterial toxin that has been made inactive but can still combine with or stimulate formation of antibodies. In many bacterial diseases, the bacteria produce a toxin that causes the disease manifestations. Heating the toxin or treating it chemically converts it into a harmless toxoid that can be injected into a human or a nonhuman animal to confer immunity from subsequent infection. The vaccines for tetanus and diphtheria are toxoids.