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': 'Smallpox vaccine was discovered by: \nSelect and explain. \nA. Edward Jenner, B. Louis pasteur, C. Salk, D. Sabin', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans: a (Edward Jenner) Ref:Ananthanarayan, ed, p. 457Early live vaccine such as Jenner's pox vaccine, were developed emperically from natural viruses.Sabin's name is related to oral polio vaccine.Salk's name is related to killed polio vaccine.This is a question based on historic importance.", 'role': 'assistant'}]