Genevac-B Vaccine Dosing
For Genevac-B (Engerix-B), administer 10 mcg (0.5 mL) to infants and children birth through 10 years, 10 mcg (0.5 mL) to adolescents 11-19 years, and 20 mcg (1.0 mL) to adults ≥20 years, using the standard 0,1, and 6-month schedule. 1
Standard Dosing by Age Group
Infants and Children (Birth through 10 years)
- Dose: 10 mcg (0.5 mL)
- Schedule: 0,1, and 6 months 1
- Route: Intramuscular in the anterolateral thigh for infants, deltoid acceptable for older children 1
Adolescents (11-19 years)
Adults (≥20 years)
Special Population Dosing
Hemodialysis Patients and Immunocompromised Adults (≥20 years)
- Dose: 40 mcg (2.0 mL) - given as two 20 mcg injections 1
- Schedule: 0,1,2, and 6 months (4-dose series) 1
- Monitoring: Annual antibody testing required; give 40 mcg booster when anti-HBs falls below 10 mIU/mL 1
This enhanced dosing for dialysis patients addresses their characteristically poor vaccine response, with only approximately 50% achieving protective titers with standard dosing 1. The 4-dose regimen with doubled doses improves seroprotection to 67% 1.
Pregnant Women
- Use Engerix-B (Genevac-B) preferentially over Heplisav-B or PreHevbrio, as safety data for the latter vaccines in pregnancy are insufficient 2
- Standard adult dosing applies: 20 mcg at 0,1, and 6 months 1
Alternate Schedules for Specific Situations
Accelerated Schedule (High-Risk Exposure)
For neonates born to HBsAg-positive mothers, recent exposure cases, or certain travelers:
- Schedule: 0,1,2, and 12 months 1
- Rationale: Achieves 99% seroprotection by month 3, with the 12-month dose providing prolonged maintenance 1
- Must also give HBIG for known/presumed exposure 1
Extended Schedule (Low-Risk Adolescents)
For children/adolescents 5-16 years with acceptable extended timing:
- Schedule: 0,12, and 24 months 1
- Note: Achieves similar final seroprotection (98.1%) but with lower GMT compared to standard schedule 1
Critical Administration Details
Route and Site
- Never inject intravenously, intradermally, or in the gluteal region - gluteal injection results in suboptimal response 1
- Infants <12 months: anterolateral thigh with 1-inch, 23-gauge needle 1
- Toddlers/children ≤10 years: deltoid with 5/8-inch, 25-gauge needle 1
- Older children/adults: deltoid with 1-inch, 23-gauge needle 1
Subcutaneous Administration
- Only for patients at hemorrhage risk (e.g., hemophiliacs) 1
- Caveat: Results in lower GMTs and increased local reactions including subcutaneous nodules 1
Interrupted Series Management
If the vaccination schedule is interrupted, do not restart the series 2. Follow these rules:
- Minimum intervals: 4 weeks between doses 1 and 2; 8 weeks between doses 2 and 3; 16 weeks between doses 1 and 3 2
- If only dose 2 delayed: give as soon as possible, ensure ≥8 weeks before dose 3
- If only dose 3 delayed: give as soon as possible
- Doses given ≤4 days before minimum interval are valid 2
Booster Dosing
Standard Populations
Hemodialysis Patients
Preparation and Handling
- Shake well before use - should appear as slightly turbid white suspension 1
- Inspect for particulate matter, discoloration, or vial cracks; discard if present 1
- Use as supplied; no dilution necessary 1
- Discard any remaining vaccine in single-dose vials 1
Evidence Quality Note
The dosing recommendations are based on FDA-approved labeling 1 and supported by 2022 ACIP guidelines 2. Clinical trial data demonstrate 98% seroconversion rates in infants and 96% seroprotection in adults at month 7 with standard dosing 1. Genevac-B has been shown equivalent in immunogenicity and tolerability to Engerix-B when administered at 6,10, and 14 weeks with DTPw vaccine 3.