A hospital nurse undergoes pre-employment screening. She recalls receiving three doses of hepatitis B vaccine in childhood. Results: HBsAg negative, anti-HBs positive (85 mIU/mL), anti-HBc negative. How should her profile be interpreted?

• A Prior occult hepatitis B infection requiring further testing
• B Resolved hepatitis B infection with natural immunity
• C Window period of acute hepatitis B
• D Vaccine-induced immunity, no further action needed ✓

Explanation

Anti-HBs above 10 mIU/mL with a negative anti-HBc indicates successful immunisation, since the recombinant vaccine contains only surface antigen and never elicits anti-core antibody. Natural infection always leaves anti-HBc behind, so an isolated positive anti-HBs cannot come from past infection. The window period shows IgM anti-HBc with neither HBsAg nor anti-HBs.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.