In 1914, the tetanus toxoid was introduced following the development of an effective therapeutic serum against tetanus by Emil Von Behring and Shibasaburo Kitasato. The vaccine consisted of a toxin-antitoxin formulation and was found to be 85 percent effective in preventing diphtheria.

Diphtheria is an acute upper respiratory illness caused by Corynebacterium diphtheriae. C. diphtheriae is a minimally invasive gram-positive bacillus that is resistant to environmental change and whose virulence is mostly confined to the secretion of an exotoxin that inhibits protein synthesis in mammalian cells