What Does a Positive Anti-HBs Result Indicate?
A positive anti-HBs result indicates immunity to hepatitis B virus (HBV) infection, either from successful vaccination or recovery from past natural infection. 1
Primary Interpretation
Anti-HBs is generally indicative of immunity to HBV infection and protection against future infection. 1 The presence of this antibody typically indicates that you are protected from hepatitis B, with immunity considered adequate when anti-HBs concentration is ≥10 mIU/mL. 1
Distinguishing the Source of Immunity
The clinical context determines whether immunity came from vaccination versus natural infection:
- Anti-HBs positive alone (without anti-HBc) = Immunity from vaccination 1, 2
- Anti-HBs positive WITH anti-HBc positive = Immunity from recovered past natural infection 1, 2
This distinction matters because persons who recover from natural HBV infection are typically positive for both anti-HBs and anti-HBc, whereas persons who respond to hepatitis B vaccine are positive only for anti-HBs. 1
Timeline and Development
Anti-HBs develops during convalescence in persons who recover from HBV infection, typically appearing within 3-4 months after HBsAg is eliminated from the blood. 1 This antibody then persists and provides long-term protection. 1
Important Clinical Caveats
Passive Transfer Situations
Anti-HBs can be detected temporarily (4-6 months) following hepatitis B immune globulin (HBIG) administration, which represents passive antibody transfer rather than true immunity. 1 This is clinically important because passively acquired anti-HBs does not confer the same long-term protection as actively acquired immunity. 3
Quantitative Threshold Matters
The protective threshold is critical: anti-HBs concentration must be ≥10 mIU/mL to indicate immunity. 1, 2 Testing should use a quantitative method that allows detection of this protective concentration. 2
Post-Vaccination Context
Transient anti-HBs positivity can occur after recent vaccination, and immunocompetent persons with anti-HBs ≥10 mIU/mL after vaccination have long-term protection and do not need further periodic testing. 2 However, testing should be performed 1-2 months after completion of the vaccination series to accurately assess immune response. 2
Special Population Considerations
- Hemodialysis patients require annual anti-HBs testing due to potential waning immunity 2
- Immunocompromised patients (HIV-infected, transplant recipients, chemotherapy patients) may need annual testing to assess anti-HBs concentrations 2
- Healthcare personnel should be tested 1-2 months after vaccination to ensure protection against occupational exposure 2