Herd immunity is not important in:

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