What is the 9, 7, 21-30 accelerated regimen for Twinrix (hepatitis A and B vaccine)?

The 0,7,21-30 Day, 12 Month Accelerated Regimen for Twinrix

The 0,7,21-30 day, 12 month schedule is an accelerated 4-dose regimen for Twinrix (combined hepatitis A and B vaccine) approved for adults ≥18 years who need rapid protection against both hepatitis A and B viruses. 1

Dosing Schedule

The accelerated regimen consists of:

• Dose 1: Day 0
• Dose 2: Day 7
• Dose 3: Days 21-30
• Dose 4 (booster): 12 months 1

Each dose contains 720 EL.U of inactivated hepatitis A antigen and 20 μg of recombinant hepatitis B surface antigen (HBsAg) in 1.0 mL. 2

Clinical Indications

This accelerated schedule is specifically designed for:

• Last-minute travelers departing to hepatitis A/B endemic regions within 1 month 3, 4
• Adults requiring rapid protection due to imminent exposure risk 1, 3
• Individuals who need protection quickly but cannot wait for the standard 0,1,6 month schedule 5

Immunogenicity and Efficacy

The accelerated schedule provides rapid seroprotection:

• At day 28-37 (after 3 doses): 63-82% seroprotection for hepatitis B and 98-100% seroconversion for hepatitis A 2, 5
• At month 13 (after booster): 96-99% seroprotection for hepatitis B and 100% seroconversion for hepatitis A 3, 2, 5

The accelerated regimen demonstrates immunogenicity at least equivalent to concurrent administration of monovalent hepatitis A and B vaccines. 2, 5

Critical Scheduling Consideration

The standard 4-day grace period for vaccine intervals does NOT apply to the first three doses of Twinrix when using the accelerated schedule. 1 This is a unique exception to standard vaccine administration rules—doses must be given on the exact days specified (0,7, and 21-30 days), not within 4 days of these intervals. 1

Comparison to Standard Schedule

The standard Twinrix schedule (0,1,6 months) provides:

• Slower initial protection but similar final seroprotection rates
• Only 3 total doses versus 4 doses for accelerated regimen 1, 4

The accelerated schedule is preferred when rapid protection is needed; the standard schedule is appropriate when there is no urgency. 3, 4

Safety Profile

The accelerated regimen is generally well tolerated with a reactogenicity profile similar to monovalent vaccines:

• Most common adverse events: injection-site pain/redness, fatigue, and headache
• Most events are mild and transient 2, 4, 5

Important Contraindications

Do not use Twinrix (any schedule) in:

• Pregnant women—use Engerix-B or Recombivax HB instead 1, 6
• Hemodialysis patients—insufficient safety/efficacy data 1
• Children <18 years—not approved for this age group 1