This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Herd immunity is not useful in - 
Select and explain. 
A. Diphtheria, B. Polio, C. Measles, D. Tetanus
D: Tetanus
Answer: D: Tetanus 
Explanation: Herd immunity has been achieved in diphtheria and poliomyelitis Small pox-herd immunity has not played a crucial role in its eradication. Tetanus- herd immunity doesn't protect the individuals ( refer pgno:103 park 23 rd edition)