What does a Hepatitis B Surface Antibody (HBsAb) quantification result of less than 3.5 IU/L and an immunity level greater than 10 mIU/mL indicate, and what intervention is needed?

Interpretation of Hepatitis B Surface Antibody Result <3.5 mIU/mL

Your Hepatitis B Surface Antibody (anti-HBs) result of <3.5 mIU/mL indicates you are not immune to hepatitis B virus infection and require vaccination. 1

Understanding Your Result

• Anti-HBs level <10 mIU/mL indicates lack of protective immunity against hepatitis B virus (HBV) infection 1
• Your result of <3.5 mIU/mL falls below the protective threshold of 10 mIU/mL 1
• This result suggests either:
  • You have never been infected with HBV and have not been vaccinated 1
  • You were previously vaccinated but your antibody levels have waned below protective levels 1

Recommended Intervention

If you have documentation of previous complete HepB vaccination:

1. Receive one challenge dose of hepatitis B vaccine 1
2. Check anti-HBs levels 4-8 weeks after this challenge dose 1
3. If anti-HBs ≥10 mIU/mL after challenge dose, no further doses needed (indicates immune memory) 1
4. If anti-HBs remains <10 mIU/mL after challenge dose, complete a second full vaccination series 1

If you have no documentation of previous HepB vaccination:

1. Complete a full hepatitis B vaccination series 1
   • HEPLISAV-B: Two-dose series at 0 and 1 month, OR
   • ENGERIX-B or Recombivax HB: Three-dose series at 0,1, and 6 months, OR
   • PreHevbrio: Three-dose series at 0,1, and 6 months 1
2. Check anti-HBs levels 1-2 months after completing the series 1

Special Considerations

• Hepatitis B vaccination is now universally recommended for all adults aged 19-59 years 1
• Certain populations have higher risk of non-response to vaccination:
  • Older individuals 1
  • Immunocompromised patients 1
  • Those with chronic conditions 1

Monitoring After Vaccination

• After completing vaccination, anti-HBs levels should be checked 1-2 months after the last dose 1
• Protective immunity is defined as anti-HBs ≥10 mIU/mL 1
• For most healthy individuals, protection persists even if antibody levels decline over time 2
• Healthcare workers and immunocompromised individuals may require periodic monitoring of anti-HBs levels 1

Common Pitfalls to Avoid

• Don't confuse anti-HBs (surface antibody) with anti-HBc (core antibody) - they indicate different things 1
• Don't assume prior vaccination guarantees immunity - antibody levels can wane over time, especially in certain populations 3
• Don't delay vaccination if indicated - hepatitis B can lead to serious liver disease 1
• Don't skip post-vaccination testing if you're in a high-risk group (healthcare workers, immunocompromised) 1