Hepatitis B Surface Antibody Positive: Interpretation
A positive Hepatitis B surface antibody (anti-HBs) test indicates protective immunity against hepatitis B virus, either from successful vaccination or recovery from natural HBV infection. 1
Primary Interpretation
Individuals with anti-HBs levels ≥10 mIU/mL are protected against HBV infection and are not infectious to others. 1 This antibody appears after viral clearance in natural infection or following successful vaccination. 1
Determining the Source of Immunity
To understand whether immunity resulted from vaccination versus natural infection, additional serologic markers are essential:
Immunity from Vaccination
- HBsAg negative + anti-HBc negative + anti-HBs positive = Immunity from vaccination 1
- These individuals have never been infected with HBV and developed immunity solely through vaccination 1
- No further HBV vaccination is required in individuals with documented positive anti-HBs 1
Immunity from Resolved Natural Infection
- HBsAg negative + anti-HBc positive + anti-HBs positive = Immunity from resolved natural infection 1
- The presence of anti-HBc indicates past HBV exposure, while anti-HBs confirms viral clearance and immunity 2, 1
- These individuals have recovered from HBV infection and are not currently infectious 3
Clinical Management Considerations
Standard Populations
- Individuals with protective anti-HBs levels (≥10 mIU/mL) typically do not require HBV vaccination 1
- They are protected against HBV infection and cannot transmit the virus to others 1
High-Risk Groups Requiring Monitoring
- Healthcare workers and other high-risk individuals should undergo periodic testing of anti-HBs levels 1
- Immunocompromised patients may warrant more frequent monitoring of anti-HBs levels 1
- Booster doses of HBV vaccine may be considered for certain high-risk individuals if anti-HBs levels fall below 10 mIU/mL 1
Special Clinical Scenarios
Pre-immunosuppression screening: Anti-HBs status is critical before initiating immunosuppressive therapy to assess HBV status and prevent reactivation 1
Post-exposure prophylaxis: Anti-HBs status determines the need for post-exposure prophylaxis after HBV exposure 1
Post-vaccination testing: Recommended for certain high-risk groups to confirm adequate immune response 1
Important Caveats
Passively Acquired Antibody
- Recent transfusion of blood products (fresh frozen plasma, immunoglobulin) can result in passively acquired anti-HBs 4
- Passively acquired anti-HBs does not confer true immunity and may lead to false reassurance 4
- Consider timing of recent transfusions when interpreting positive anti-HBs results, particularly in patients who subsequently develop hepatitis B 4
Waning Immunity Concerns
- Anti-HBs levels can decrease below protective levels years after natural infection or vaccination 5
- However, immune memory may persist even when anti-HBs becomes undetectable, particularly after natural infection 5
- The clinical significance of declining anti-HBs levels in previously immune individuals remains debated 5
Reactivation Risk in Resolved Infection
- Individuals with anti-HBc positive + anti-HBs positive (resolved infection) face a 3-45% risk of HBV reactivation when receiving immunosuppressive therapy, particularly with anti-CD20 monoclonal antibodies or high-dose corticosteroids 3
- HBV DNA testing before immunosuppressive therapy helps define reactivation risk 3
- Antiviral prophylaxis may be warranted in these patients despite positive anti-HBs 3