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': 'The following are live attenuated vaccine, except- \nSelect and explain. \nA. Oral poilio, B. Yellow fever, C. Measles, D. Influenza', 'role': 'user'}, {'content': 'Answer: A \nExplanation: oral polio vaccines were first introduced by Sabin in 1957.it contains live attenuated strains of virus type 1,2, and 3.grown in primary monkey kidney or h7man diploid cell cultureref;parks tectbook,ed22,pg 187', 'role': 'assistant'}]