Hepatitis B Surface Antibody Reactive: Meaning and Interpretation
A reactive (positive) hepatitis B surface antibody (anti-HBs) indicates immunity to hepatitis B virus, either from successful vaccination or recovery from a past natural infection. 1
What This Result Means
You are immune to hepatitis B and cannot be infected with the virus under normal circumstances. 1 The presence of anti-HBs demonstrates that your immune system has developed protective antibodies against the hepatitis B surface antigen, providing ongoing protection. 1
Two Possible Sources of Immunity
Your immunity comes from one of two scenarios:
1. Vaccination-Derived Immunity
- If you have anti-HBs positive with negative hepatitis B core antibody (anti-HBc), this confirms immunity from vaccination. 2, 3
- This pattern (HBsAg negative, anti-HBs positive, anti-HBc negative) is the classic signature of vaccine-induced protection. 3
- Current assays detect protective immunity when anti-HBs levels are ≥10 mIU/mL. 3
2. Natural Immunity from Past Infection
- If you have anti-HBs positive with positive anti-HBc, this indicates you recovered from a past hepatitis B infection and now have natural immunity. 3, 4
- This pattern (HBsAg negative, anti-HBs positive, anti-HBc positive) shows resolved infection with clearance of the virus. 3
- You are not currently infectious and cannot transmit the virus to others. 4
Clinical Significance
In most patients with self-limited acute HBV infection, HBsAg and anti-HBs are not detectable simultaneously in serum or plasma. 1 This means you have cleared the active infection if you previously had one.
Protection Level
- Anti-HBs provides functional immunity independent of the antibody level once immunologic memory is established. 5
- Even if antibody levels decline over time, immunologic memory persists and provides ongoing protection for 5-12 years or longer after vaccination. 5
- Memory B lymphocytes remain capable of producing anti-HBs even when circulating antibody levels fall. 5
Important Caveats
Rare Pitfall: Passively Acquired Antibody
- If you recently received blood products, fresh frozen plasma, or hepatitis B immune globulin, the anti-HBs may be passively acquired rather than indicating true immunity. 6
- Passively acquired antibody does not confer lasting protection and will decline without providing immunologic memory. 6
- This is uncommon but should be considered if you have recent transfusion history. 6
Special Populations Requiring Monitoring
Immunosuppressed Patients:
- If you require immunosuppressive therapy (particularly anti-CD20 antibodies like rituximab or high-dose corticosteroids), you may need monitoring even with positive anti-HBs. 2, 4
- Patients with anti-HBc positive (natural immunity) have a 3-45% risk of HBV reactivation during immunosuppression. 4
- Those with vaccine-derived immunity (anti-HBc negative) have minimal reactivation risk. 2
Dialysis Patients:
- Annual anti-HBs screening may be recommended in dialysis units due to higher exposure risk. 2
No Further Action Needed for Most People
For immunocompetent individuals, no routine booster vaccination or additional testing is required. 2 Your positive anti-HBs confirms adequate protection against hepatitis B infection through either vaccination or past resolved infection.