Which serologic marker indicates Hepatitis B immunity due to vaccination or prior infection?

• A. HBsAg positive
• B. Anti-HBs positive
• C. Anti-HBc positive
• D. Anti-HBs negative

Answer: (B)

In Hepatitis B serology, protection is shown by the antibody to the surface antigen. When anti-HBs is present, you have immunity to Hepatitis B, which can come from either vaccination or recovery from a prior infection. HBsAg being positive means an active infection, not immunity. Anti-HBc indicates past exposure to the virus, but alone it does not prove immunity. If anti-HBs is present with anti-HBc, that usually reflects prior natural infection with lasting immunity; if anti-HBs is present but anti-HBc is negative, that points to immunity from vaccination. Thus, anti-HBs is the marker that best indicates Hepatitis B immunity from vaccination or prior infection.