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: Social & Preventive Medicine
[{'content': 'You have given ViPS vaccine to a person. How often will you ask him to take booster doses? \nSelect and explain. \nA. Every year, B. Every 2 year, C. Every 3 year, D. Every 4 year', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The injectable typhoid vaccine ViPS is a single dose vaccine which requires booster doses every 3 year. Ty21a vaccine is the oral typhoid vaccine. 3 doses are taken on day 1,3 and 5. It is effective for up to 7 years after last dose. It is recommended in people travelling to endemic areas and during out breaks. Ref: Park, Edition 21, Page - 215', 'role': 'assistant'}]