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': 'Which is the following is/are subunit vaccines \nSelect and explain. \nA. Typhoid Vi, B. H. Influevza vaccine (Hib), C. Hepatitis B Vaccine, D. Diphtheria', 'role': 'user'}, {'content': 'Answer: A \nExplanation: This subunit vaccine is composed of purified VI capsular polysaccharide from the Ty2 S. Subcutaneously or intramuscularly. Stable for 6 months Only 1 dose is required and vaccine confers protection 7 days after injection. (refer pgno:237 park 23 rd edition)', 'role': 'assistant'}]