This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Concept of Control, Subject name: Social & Preventive Medicine
[{'content': 'Vaccine is what level of prevention: \nSelect and explain. \nA. Primordial, B. Primary, C. Secondary, D. Tertiary', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) PrimaryRef: K. Park 23rd ed. / 41, 370-74* All vaccines/immunization are primary level of prevention.* Refer to above table.', 'role': 'assistant'}]