Infection Control · single question
A dental staff member's serology returns ANTI-HBs POSITIVE with negative HBsAg and negative anti-HBc. What does this indicate?
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Correct answer: C. Immunity from vaccination
- A. Resolved natural infection would show anti-HBs POSITIVE AND anti-HBc POSITIVE, because natural infection exposes the immune system to the core antigen as well.
- B. Acute infection shows HBsAg positive with IgM anti-HBc positive.
- C. Correct. Isolated ANTI-HBs POSITIVITY with negative anti-HBc means IMMUNITY FROM VACCINATION. The hepatitis B vaccine contains only surface antigen, so it generates anti-HBs alone — it never produces core antibody. A titre of at least 10 mIU/mL confirms protection. This distinction is examined constantly: anti-HBs alone equals vaccinated; anti-HBs PLUS anti-HBc equals resolved natural infection.
- D. Chronic carriage shows persistent HBsAg positivity beyond six months.
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