Toxoid is devoid of toxicity but is virtually indistinguishable antigenically from toxin. In the U.S. two doses are given one month apart to infants 3-4 months of age with a booster one year later. Current vaccines use a DT with specific mutations that render it non-enzymatically active. Toxin is produced from same the strain isolated in 1896. Strain lacks secreted sideropore, corynebactin.
Vaccine is extremely effective that requires public health policies and compliance.
An example of breakdown in public health policies is currently occuring in Russia where there have been major recent outbreaks of Diphtheria. Because this problem was essentially solved so early in the history of microbiology, many unanswered questions regarding pathogenesis and immunity remain. What is the role of the toxin in pathogenesis. How does antibody to toxin protect against local infection.