Anti-HBs? Tells us if:

• A. if immune due to previous infection or vaccination
• B. Acive HBV
• C. Not immune
• D. Unknown

Answer: (A)

Anti-HBs are antibodies to the hepatitis B surface antigen. Their presence indicates protective immunity to hepatitis B, produced either after vaccination or after recovery from a past infection. They do not signify an active infection—that would be indicated by the surface antigen (HBsAg) or detectable HBV DNA. To distinguish the source of immunity, you’d look at other markers: anti-HBc helps differentiate natural infection (anti-HBc positive, possibly with anti-HBs) from vaccination-induced immunity (anti-HBs positive, anti-HBc negative). In short, anti-HBs tells you whether someone is immune, regardless of whether that immunity came from vaccination or prior infection. If anti-HBs is absent, the person is not immune and may need vaccination.