What is the recommended course of action for a patient with a low Anti-HBs (Antibody to Hepatitis B surface antigen) result of 1.13 mIU/mL, indicating inadequate immunity to Hepatitis B?

Management of Low Anti-HBs Level (1.13 mIU/mL)

Administer a single booster dose of hepatitis B vaccine immediately, then retest anti-HBs 1-2 months later to determine if additional doses are needed. 1

Understanding Your Result

Your anti-HBs level of 1.13 mIU/mL is below the protective threshold of 10 mIU/mL, indicating inadequate immunity to hepatitis B virus. 1, 2 This makes you a "non-responder" to the initial vaccine series and susceptible to HBV infection. 1

Recommended Management Algorithm

Step 1: Single Booster Dose First

• Give one dose of hepatitis B vaccine now (standard adult dose: 20 mcg for Engerix-B). 1
• This approach is more practical than immediately starting a complete second series. 1
• Wait 1-2 months after this dose, then retest anti-HBs. 1

Step 2: Interpret Post-Booster Results

If anti-HBs ≥10 mIU/mL after the single booster:

• You are now protected and no further doses are needed. 1
• Document this response for future reference. 1

If anti-HBs remains <10 mIU/mL after the single booster:

• Complete a full second 3-dose vaccine series (total of 6 doses counting your original series). 1
• Administer the remaining 2 doses on an appropriate schedule (typically at 1 and 6 months after the booster). 1
• Retest anti-HBs 1-2 months after the final dose of the second series. 1

Step 3: If Still Non-Responsive After Complete Second Series

If anti-HBs remains <10 mIU/mL after two complete vaccine series:

• Test for HBsAg to rule out chronic HBV infection. 1
• If HBsAg-negative, you are considered a true non-responder (occurs in approximately 5-10% of healthy adults). 3
• You will need hepatitis B immune globulin (HBIG) for any future known exposure to HBV. 1
• No additional vaccine doses are recommended beyond two complete series. 1

Why Not Restart Immediately?

The CDC guidelines specifically recommend the single-dose approach first because 44-100% of initial non-responders will achieve protective levels after just one additional dose. 2 This avoids unnecessary injections and is more cost-effective than immediately restarting a full series. 1

Special Considerations

Higher-dose vaccine may be needed if:

• You are on hemodialysis (40 mcg dose recommended). 1, 3
• You are immunocompromised (40 mcg dose may be considered). 1

Important caveats:

• Ensure you actually completed the original 3-dose series before proceeding with revaccination. 1
• The protective threshold is definitively ≥10 mIU/mL, not higher values sometimes mentioned in older literature. 1, 2
• If you are a healthcare worker or have occupational exposure risk, document your vaccination response status for future exposure management. 1

Timeline Summary

• Now: Single booster dose
• 1-2 months later: Retest anti-HBs
• If still <10 mIU/mL: Complete 2 additional doses (months 1 and 6 after booster)
• 1-2 months after final dose: Final anti-HBs testing

This stepwise approach maximizes your chance of achieving protection while minimizing unnecessary vaccinations. 1, 2