How should Twinrix (hepatitis A and B vaccine) be administered?

How Twinrix is Administered

Twinrix is given as a 1-mL intramuscular injection into the deltoid muscle, using either a standard 3-dose schedule (0,1, and 6 months) or an accelerated 4-dose schedule (days 0,7,21-30, and month 12). 1

Route and Site of Administration

• Intramuscular injection only - never give intravenously, intradermally, or subcutaneously 2
• Deltoid muscle - this is the required injection site 2
• Avoid gluteal region - injections in the buttocks result in suboptimal immune response 2

Dosing Schedules

Standard Schedule (Most Common)

Three doses of 1 mL each at 0,1, and 6 months 1, 2

This is the typical regimen for routine vaccination in adults ≥18 years.

Accelerated Schedule (For Rapid Protection)

Four doses of 1 mL each: Days 0,7,21-30, followed by a booster at month 12 3, 2

This accelerated regimen is specifically designed for:

• Pre-travel vaccination when departure is imminent
• Situations requiring rapid immunity against hepatitis A and B 3

The accelerated schedule provides faster initial protection, with 63.2% achieving hepatitis B seroprotection by day 37 compared to 43.5% with standard monovalent vaccines 4. However, the 12-month booster dose is essential for long-term protection.

Preparation Before Injection

The vaccine requires proper resuspension before administration 2:

1. Hold syringe upright in closed hand
2. Shake by tipping upside down and back upright
3. Repeat vigorously for at least 15 seconds
4. Inspect - should appear as uniform hazy white suspension (not clear)
5. If not uniform, repeat shaking for another 15 seconds

Critical pitfall: A clear appearance indicates inadequate mixing - the vaccine must appear as a uniform hazy white suspension before use 2.

Important Scheduling Notes

• If the series is interrupted, do not restart - simply continue where you left off 1
• For 3-dose series: minimum 4 weeks between doses 1 and 2; minimum 8 weeks between doses 2 and 3; minimum 16 weeks between doses 1 and 3 1
• Exception for accelerated schedule: The standard 4-day grace period does NOT apply to the first 3 doses of the accelerated regimen 1

Special Populations

Pregnant women: Twinrix is safe to use during pregnancy (unlike Heplisav-B or PreHevbrio which lack pregnancy safety data) 1

Hemodialysis patients: Standard Twinrix dosing is appropriate; unlike single-antigen hepatitis B vaccines, no high-dose formulation exists for Twinrix 1