Hepatitis B Post-Exposure Prophylaxis
For unvaccinated persons exposed to HBsAg-positive blood, immediately administer both HBIG (0.06 mL/kg) and hepatitis B vaccine simultaneously at separate anatomic sites, preferably within 24 hours of exposure. 1
Management Algorithm Based on Source and Vaccination Status
HBsAg-Positive Source Exposure
Unvaccinated persons:
- Give HBIG (0.06 mL/kg IM) as soon as possible, ideally within 24 hours 1, 2
- Simultaneously administer first dose of hepatitis B vaccine at a separate injection site (different limb) 1, 2
- Complete the 3-dose vaccine series at 0,1, and 6 months 2
- Critical timing: Effectiveness diminishes after 7 days for percutaneous exposures and 14 days for sexual exposures 1
Previously vaccinated persons (incomplete series):
- Give HBIG (0.06 mL/kg) and complete the remaining vaccine doses 1
- Do not restart the series—simply continue where they left off 2
Previously vaccinated persons (complete series, no post-vaccination testing):
Previously vaccinated with documented immunity (anti-HBs ≥10 mIU/mL):
- No treatment required—these individuals are considered protected 1
HBsAg-Unknown Source Exposure
Unvaccinated persons:
- Initiate hepatitis B vaccine series with first dose as soon as possible (preferably within 24 hours) 2
- Complete the series at 0,1, and 6 months
- HBIG is NOT indicated for unknown source exposures 1, 2
Previously vaccinated persons (incomplete series):
Previously vaccinated persons (complete series):
- No further treatment required 2
Key Clinical Considerations
Timing is Critical
The evidence consistently shows that prophylaxis effectiveness decreases significantly with delayed administration. While the optimal window is within 24 hours, prophylaxis may still provide benefit up to 7 days for percutaneous exposures (needlestick, bite) and up to 14 days for sexual exposures 1, 2. One study from Korea suggests HBIG given between 24 hours and 7 days may be as effective as administration within 24 hours 3, though this should not delay urgent treatment.
Administration Technique
HBIG and vaccine must be given at separate anatomic sites (e.g., different limbs) when administered simultaneously 1, 2. Research in mice suggests same-site administration may reduce vaccine immunogenicity 4, though the clinical significance in humans requires further study. The current guideline recommendation for separate sites should be strictly followed.
Dosing Specifics
- HBIG dose: 0.06 mL/kg body weight IM 1, 5
- Vaccine dose: Age-appropriate (typically 20 μg for adults, 10 μg for children) 5
- For sexual exposures to HBsAg-positive persons: Same regimen applies if started within 14 days of last contact 5
Common Pitfalls to Avoid
Don't delay waiting for source testing: If source HBsAg status is unknown and cannot be determined rapidly, start the vaccine series immediately—you can always stop if source tests negative 2
Don't restart vaccine series unnecessarily: For partially vaccinated individuals, simply complete the remaining doses rather than restarting 2
Don't give HBIG for unknown sources: This is a waste of resources and not indicated by guidelines 1, 2
Don't forget post-vaccination testing for high-risk groups: Healthcare workers, immunocompromised persons, and sexual partners of HBsAg-positive individuals should undergo serologic testing 1-2 months after series completion 2, 1
Special Populations
Healthcare workers with occupational exposure: Follow the same algorithm but ensure post-vaccination testing is performed 1-2 months after the final vaccine dose to document protective antibody levels (≥10 mIU/mL) 6
Infants born to HBsAg-positive mothers: Administer HBIG (0.5 mL) within 12 hours of birth along with first vaccine dose at separate site; efficacy decreases markedly if delayed beyond 48 hours 5
The evidence strongly supports that combined passive-active prophylaxis (HBIG + vaccine) is more effective than vaccine alone for HBsAg-positive exposures 7, with one study showing infection rates of 4% with combination therapy versus 33% with HBIG alone (p<0.02).