This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Herd immunity is not important in: 
Select and explain. 
A. Tetanus, B. Pertussis, C. Diphtheria, D. All
A: Tetanus
Answer: A: Tetanus 
Explanation: The epidemics wave declines with a up-built of herd immunity after natural infection and if high level immunity maintained with immunization disease eliminated, e.g. Polio, Diphtheria. It is neither possible nor necessary to achieve 100% herd immunity. In a population to halt an epidemic or to control disease. E.g. small pox eradication.
In the case of tetanus it does not protect the individual.
Epidemiology of Infectious
Diseases