This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'The following vaccine is developed against cholera - \nSelect and explain. \nA. Dukoral, B. Vi polysaccharide, C. Ty 21a oral, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Two types of oral cholera vaccines : Dukoral and Sanchol Vi polysaccharide and Ty 21a oral are typhoid vaccines. Ref: PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 23rd edition , Page :233', 'role': 'assistant'}]