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: Medicine
In a patient, only Anti HBsAg is positive in serum. All other viral markers are negative. This indicates: 
Select and explain. 
A. Acute hepatitis, B. Chronic active hepatitis, C. Persistent carrier, D. Immunized person with Hepatitis B vaccine
D: Immunized person with Hepatitis B vaccine
Answer: D: Immunized person with Hepatitis B vaccine 
Explanation: None