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': 'Vaccine in the UPI which aims at preventing blindness is - \nSelect and explain. \nA. Measles, B. Rubella, C. DPT, D. Polio', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Measles blindness is the single leading cause of blindness among children in low-income countries, accounting for an estimated 15,000 to 60,000 cases of blindness per year.', 'role': 'assistant'}]