This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Vaccination causing intussusception - \nSelect and explain. \nA. Rotavirus, B. Parvovirus, C. Poliovirus, D. BCG', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In 1999, a highly efficacious rotavirus vaccine, Rotashield licensed in the United States, was withdrawn from the market after less than one year because of its association with intussusception.', 'role': 'assistant'}]