A patient's lab results show isolated Hepatitis B surface antibody (Anti-HBs) positivity, with Hepatitis B core antibody (Anti-HBc) negative. What does this most likely indicate?

The patient is vaccinated against Hepatitis B
The patient currently has an active Hepatitis B infection
The patient has chronic Hepatitis B
The test result is invalid and must be repeated

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Correct answer: A. The patient is vaccinated against Hepatitis B

Isolated Anti-HBs positivity (without Anti-HBc positivity) reflects immunity from vaccination, since the Hepatitis B vaccine contains only surface antigen (HBsAg) and induces only an Anti-HBs response. By contrast, past natural infection (resolved) typically shows BOTH Anti-HBs AND Anti-HBc positive, since natural infection exposes the immune system to core antigen as well.

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A patient's lab results show isolated Hepatitis B surface antibody (Anti-HBs) positivity, with Hepatitis B core antibody (Anti-HBc) negative. What does this most likely indicate?

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