What is HBIG (Hepatitis B Immune Globulin)?
HBIG is a purified human plasma-derived immunoglobulin solution containing high concentrations of antibodies against hepatitis B surface antigen (anti-HBs) that provides immediate passive immunity against hepatitis B virus infection. 1, 2
Composition and Mechanism
HBIG is manufactured from pooled plasma donated by individuals with high anti-HBs titers, processed through cold ethanol fractionation and multiple viral inactivation steps. The product contains 15-18% protein solution with anti-HBs antibody potency equivalent to or exceeding 220 international units (IU) per mL 2.
The mechanism of action involves:
- Neutralizing circulating hepatitis B virus particles
- Blocking viral entry and binding to hepatocytes
- Potentially targeting HBV-infected cells through antibody-mediated immune responses 3
Duration of Protection
HBIG provides temporary passive immunity lasting 3-6 months 1. Detectable anti-HBs levels typically persist for approximately 2 months or longer after administration, with mean half-life between 17.5 and 25 days 2. Passively acquired anti-HBs can be detected for 4-6 months after HBIG administration 1.
Primary Clinical Indications
HBIG is used as an adjunct to hepatitis B vaccine, not as standalone prophylaxis in most situations 1. The main indications are:
1. Perinatal Exposure (Most Critical)
- Infants born to HBsAg-positive mothers receive 0.5 mL HBIG within 12 hours of birth (preferably), administered at a separate anatomical site from the vaccine 1, 2
- Efficacy decreases markedly if delayed beyond 48 hours 2
- Must be combined with hepatitis B vaccine series
2. Percutaneous/Mucosal Exposure
- For unvaccinated persons exposed to HBsAg-positive blood: HBIG immediately plus initiate vaccine series 2
- For vaccinated persons with inadequate antibody response: HBIG immediately plus vaccine booster 2
- Effectiveness diminishes significantly if not initiated within 7 days of exposure 4
3. Sexual Exposure
- Single dose of 0.06 mL/kg within 14 days of last sexual contact with HBsAg-positive person 2
- Combined with hepatitis B vaccine series initiation
4. Liver Transplantation
- Used long-term to prevent HBV recurrence post-transplant in patients with HBV-related liver disease 3, 5
- Often combined with oral nucleoside/nucleotide analogues
Critical Administration Details
HBIG must be administered intramuscularly only—never intravenously 2. When given with hepatitis B vaccine, the two products must be administered at separate anatomical sites to avoid interference 1, 2.
Important Caveats
- HBIG can temporarily suppress the immune response to hepatitis B vaccine when co-administered, particularly in newborns, though memory B-cell responses remain intact 6
- For infants born to HBsAg-positive mothers, post-series serologic testing is essential to confirm seroprotection 6
- HBIG is not indicated for treatment of acute or chronic hepatitis B—only for prophylaxis 7
- Viral escape mutations (Y134S, P142S, G145R) can reduce HBIG binding efficacy, though this is primarily a concern in transplant settings 8