Herd immunity has been deemed instrumental in rapid disease eradication. What is the minimum percentage of children which needs to be vaccinated successfully, in order to achieve herd immunity to diphtheria?

Herd immunity can only be achieved in those diseases which depend on human transmission, such as diphtheria. Thus, in the case of tetanus, active immunization is of benefit to the individual, but not to the community, since it will not eliminate the organism which is found in the feces of domestic animals and persists in soil as highly resistant spores.