What is the recommended weight‑based dose and administration schedule of hepatitis B immune globulin for post‑exposure prophylaxis in adults and children?

Hepatitis B Immunoglobulin Dosing for Post-Exposure Prophylaxis

Standard Weight-Based Dose

The recommended dose of hepatitis B immune globulin (HBIG) for post-exposure prophylaxis is 0.06 mL/kg body weight administered intramuscularly as soon as possible after exposure, preferably within 24 hours. 1, 2

• This weight-based dosing applies universally to adults, children, and infants exposed to HBsAg-positive sources. 1
• The maximum single dose is typically 5 mL in adults. 1
• HBIG should be administered at a separate anatomic site from the hepatitis B vaccine when given simultaneously. 1

Administration Schedule by Exposure Type

Percutaneous or Mucosal Exposure to HBsAg-Positive Source

For unvaccinated persons or vaccine non-responders:

• Administer HBIG (0.06 mL/kg) immediately, preferably within 24 hours of exposure. 1
• Simultaneously initiate hepatitis B vaccine series at a separate injection site. 1
• Complete the vaccine series using age-appropriate dosing at 0,1, and 6 months. 1

For partially vaccinated persons:

• Give HBIG (0.06 mL/kg) immediately and complete the remaining vaccine doses. 1

For fully vaccinated persons with unknown antibody response:

• Administer a single vaccine booster dose; HBIG is not required. 1

For documented vaccine responders (anti-HBs ≥10 mIU/mL):

• No HBIG or additional vaccine doses are needed. 1

Sexual Exposure to HBsAg-Positive Person

• Administer HBIG 0.06 mL/kg as a single intramuscular dose within 14 days of last sexual contact. 2
• Begin hepatitis B vaccine series simultaneously at a different site. 2
• The vaccine series should be completed even if sexual contact continues. 2

Perinatal Exposure (Infants Born to HBsAg-Positive Mothers)

Critical timing considerations:

• Administer HBIG 0.5 mL intramuscularly to the newborn within 12 hours of birth for maximum efficacy. 2
• Efficacy decreases markedly if treatment is delayed beyond 48 hours. 1, 2
• HBIG can be given up to 72 hours after birth but with reduced effectiveness. 1

Concurrent vaccination:

• Give the first dose of hepatitis B vaccine (10 μg) within 7 days of birth at a separate injection site. 2
• Complete the vaccine series at 1 month and 6 months of age. 2
• If the first vaccine dose is delayed beyond 3 months, repeat the 0.5 mL HBIG dose at 3 months. 2

Household Exposure

• Infants <12 months of age exposed to a primary caregiver with acute hepatitis B should receive HBIG 0.5 mL plus hepatitis B vaccine. 2
• Other household contacts require prophylaxis only if they had identifiable blood exposure (e.g., sharing toothbrushes or razors), which should be managed as sexual exposure. 2

Special Circumstances

Vaccine Non-Responders After Complete Series

For persons who failed to respond to two complete vaccine series (six total doses):

• Administer HBIG 0.06 mL/kg immediately after any known HBsAg-positive exposure. 1
• Give a second dose of HBIG one month later. 2
• These individuals remain permanently susceptible and require HBIG for each future exposure. 1

Exposure to Unknown HBsAg Status Source

• Unvaccinated persons should receive the hepatitis B vaccine series starting immediately. 1
• HBIG is not routinely recommended unless the source is later confirmed HBsAg-positive. 1
• If the source is high-risk and testing is unavailable, consider HBIG administration for vaccine non-responders. 1

Timing Window for HBIG Administration

Optimal timing:

• HBIG should be administered as soon as possible, ideally within 24 hours of exposure for maximum protection. 1, 2

Acceptable delayed administration:

• HBIG retains protective efficacy when given up to 7 days post-exposure, though effectiveness may be reduced. 3
• For perinatal exposure, administration beyond 48 hours shows markedly decreased efficacy. 1, 2
• For sexual exposure, HBIG can be given up to 14 days after last contact. 2

Route of Administration

• HBIG must be administered intramuscularly; intravenous injection is contraindicated. 2
• The deltoid muscle is the preferred site in adults and older children. 1
• The anterolateral thigh is preferred for infants and young children. 1

Common Pitfalls to Avoid

• Never delay HBIG administration while waiting for source testing results if the exposure is high-risk; prophylaxis effectiveness declines rapidly after 24 hours. 1, 2
• Never administer HBIG intravenously; it is formulated exclusively for intramuscular use. 2
• Never inject HBIG and hepatitis B vaccine at the same anatomic site; use separate injection sites to avoid interference. 1
• Never omit HBIG in newborns of HBsAg-positive mothers even if birth occurs outside the hospital; arrange urgent administration within 12 hours. 2
• Never assume fully vaccinated persons are protected without documented anti-HBs testing; those with unknown response should receive a vaccine booster after exposure. 1
• Never give only HBIG without initiating the vaccine series in previously unvaccinated persons; combined passive-active prophylaxis provides both immediate and long-term protection. 1, 4