What is the recommended hepatitis B post‑exposure prophylaxis (PEP) after a needlestick injury, based on the source's hepatitis B surface antigen (HBsAg) status and the exposed person's hepatitis B vaccination and anti‑HBs antibody level?

Hepatitis B Post-Exposure Prophylaxis After Needlestick Injury

For an unvaccinated or incompletely vaccinated person with a needlestick injury from an HBsAg-positive source, immediately administer both HBIG (0.06 mL/kg intramuscularly) and the first dose of hepatitis B vaccine at separate anatomic sites, preferably within 24 hours of exposure. 1, 2, 3

Management Algorithm Based on Vaccination Status and Source HBsAg Status

If Source is HBsAg-Positive:

Unvaccinated or Incompletely Vaccinated Person:

• Administer HBIG 0.06 mL/kg intramuscularly immediately (preferably within 24 hours, effectiveness decreases markedly after 7 days) 1, 3
• Simultaneously give first dose of hepatitis B vaccine at a separate anatomic site 1, 2, 3
• Complete the full 3-dose vaccine series at 0,1, and 6 months 2, 4
• Perform anti-HBs testing 1-2 months after completing the vaccine series, but delay this testing until 4-6 months post-exposure if HBIG was given (to avoid detecting passive antibodies from HBIG) 1, 2, 3

Previously Vaccinated with Known Immunity (anti-HBs ≥10 mIU/mL):

• No treatment required - documented immunity provides complete protection 1, 2

Previously Vaccinated with Unknown Immunity Status:

• Immediately administer HBIG 0.06 mL/kg and one vaccine booster dose at separate sites without waiting for antibody test results 1, 2, 4
• Draw baseline blood for anti-HBs testing, but do not delay prophylaxis while awaiting results 2
• Test anti-HBs 4-6 months after HBIG administration to determine true immune status 1, 2

Known Vaccine Non-Responder (completed 6 doses, anti-HBs <10 mIU/mL):

• Administer HBIG 0.06 mL/kg immediately 1
• Give a second dose of HBIG one month later (total of 2 doses) 1, 5, 3
• No additional vaccination needed for documented non-responders after two complete vaccine series 1

If Source HBsAg Status is Unknown:

Unvaccinated or Incompletely Vaccinated Person:

• Begin hepatitis B vaccine series immediately (first dose within 24 hours) 1
• No HBIG indicated unless source is determined to be high-risk 1
• Complete the full vaccine series 1

Previously Vaccinated Person:

• No treatment required 1

If Source is HBsAg-Negative:

• No HBIG or additional vaccination needed regardless of vaccination status 1

Critical Timing Considerations

The 24-hour window is crucial - HBIG should be administered as soon as possible after exposure, preferably within 24 hours 1, 2, 3. The effectiveness of HBIG decreases significantly when given beyond 7 days after percutaneous exposure 1, 2. This narrow therapeutic window makes immediate action essential, even before serologic test results are available 2.

Administration Details

• HBIG dose: 0.06 mL/kg body weight, administered intramuscularly (typically in the deltoid muscle) 1, 5, 3
• Hepatitis B vaccine and HBIG must be given at separate anatomic sites to ensure optimal immune response 1, 2, 3
• For very large adults, maximum single HBIG volume is limited to 5 mL despite weight-based calculations 2

Follow-Up Testing Protocol

Baseline testing: Draw blood immediately for HBsAg and anti-HBs to establish baseline status, but do not delay prophylaxis 2, 4

Post-vaccination testing timing:

• If HBIG was not given: Test anti-HBs 1-2 months after completing vaccine series 1, 2
• If HBIG was given: Delay testing until 4-6 months after HBIG administration to avoid detecting passively transferred antibodies 1, 2, 3

Protective immunity is defined as anti-HBs ≥10 mIU/mL 1, 2

Common Pitfalls to Avoid

• Never delay HBIG administration while awaiting serologic test results - the risk of not treating someone who lacks immunity far outweighs the cost of treating someone who may already be protected 2
• Do not assume immunity without documented serologic testing after vaccination 2
• Do not fail to complete the full vaccine series after initial post-exposure management 2, 4
• Do not test for anti-HBs too early after HBIG administration - wait 4-6 months to avoid detecting passive antibodies 1, 2, 5
• Do not administer HBIG and vaccine at the same anatomic site - use separate sites to ensure optimal response 2, 5

Source Patient Assessment

Immediately test the source patient for HBsAg to guide prophylaxis decisions 2, 4. When the source cannot be tested, management should be based on estimated risk of HBV exposure - high-risk unknown sources should be treated as HBsAg-positive 2, 3.