Does a reactive hepatitis B (HB) surface antibody indicate immunity to hepatitis B in a patient?

Hepatitis B Surface Antibody Reactive: Immunity Interpretation

Yes, a reactive hepatitis B surface antibody (anti-HBs) typically indicates immunity to hepatitis B virus, protecting the patient from HBV infection. 1

Understanding Anti-HBs Positivity

The presence of anti-HBs typically indicates immunity from HBV infection, whether acquired through natural infection or vaccination. 1 The key distinction lies in the complete serologic profile:

Immunity from Vaccination

• Anti-HBs positive alone (without anti-HBc) indicates vaccine-derived immunity 1, 2
• Antibody titers ≥10 mIU/mL against HBsAg are recognized as conferring protection against hepatitis B 3
• Persons who respond to hepatitis B vaccine have only anti-HBs present 1
• Infection or immunization with one genotype of HBV confers immunity to all genotypes 1

Immunity from Natural Infection

• Anti-HBs positive with anti-HBc positive indicates immunity from resolved natural infection 1, 4
• The majority of persons who recover from natural infection will be positive for both anti-HBs and anti-HBc 1
• In persons who recover from HBV infection, HBsAg is eliminated from the blood (usually within 3-4 months), and anti-HBs develops during convalescence 1

Critical Caveats and Pitfalls

Passively Acquired Antibody

• Anti-HBs can be detected for several months after hepatitis B immune globulin (HBIG) administration and does not represent true immunity 1
• Passively acquired anti-HBs from blood products does not confer protection against HBV infection 5
• This is a critical pitfall in patients who have received recent transfusions or HBIG 5

Transient Post-Vaccination Positivity

• Transient HBsAg positivity (not anti-HBs) has been reported for up to 18 days after vaccination and is clinically insignificant 1

Rare Non-Protective Anti-HBs

• In extremely rare cases, anti-HBs antibodies may be present but not protective, particularly when directed against only a subdeterminant of HBsAg or arising from cross-reaction 6
• Anti-HBs positivity in the absence of anti-HBc (when not from vaccination) may rarely represent non-protective antibodies 6

Special Populations Requiring Monitoring

Immunosuppressed Patients

• Patients with anti-HBc positive (resolved infection) have a 3-45% risk of HBV reactivation when receiving immunosuppressive therapy, even if anti-HBs is present 4
• Those receiving high-risk immunosuppression (anti-CD20/CD52 antibodies, high-dose corticosteroids) require HBV DNA testing and potential antiviral prophylaxis 7, 4

Hemodialysis Patients

• Dialysis patients may lose immunity over time and require annual anti-HBs screening 7, 8
• Anti-HBs titers decrease faster in vaccinated HD patients compared to those with naturally acquired immunity 8
• HD patients who lose vaccine-derived immunity should receive booster doses when anti-HBs falls below 10 mIU/mL 8

Healthcare Workers

• Healthcare workers and those with ongoing HBV exposure risk require periodic anti-HBs screening to monitor for loss of immunity 7

Clinical Algorithm for Interpretation

When anti-HBs is reactive, determine:

1. Check HBsAg status - If positive, patient has active infection despite anti-HBs presence (extremely rare) 1

2. Check anti-HBc status 1, 2

   • Anti-HBc negative = Vaccine-derived immunity (minimal reactivation risk)
   • Anti-HBc positive = Natural immunity from resolved infection (higher reactivation risk with immunosuppression)

3. Assess for passive antibody - Recent HBIG or transfusion within past several months negates protective interpretation 1, 5

4. Consider special populations - Dialysis patients, immunosuppressed patients, and healthcare workers may need ongoing monitoring despite positive anti-HBs 7, 4, 8