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
[{'content': 'All vaccine are given in disaster, except- \nSelect and explain. \nA. Cholera, B. Influenza, C. Measles, D. Tetanus', 'role': 'user'}, {'content': "Answer: A \nExplanation: Park's textbook of preventive and social medicine * Mass chemoprophylaxis is not advised for the total community in order to prevent one serious case of cholera because some 10000 persons must be given the drug,drug effect is only sho lived and whenever mass chemoprophylaxis attempted it failed to stop the spread of cholera.", 'role': 'assistant'}]