What is the recommended dosage schedule for Twinrix (hepatitis A and hepatitis B vaccine)?

Twinrix Dosage Schedule

For adults ≥18 years, administer Twinrix as 1 mL intramuscularly using either the standard 3-dose schedule at 0,1, and 6 months OR the accelerated 4-dose schedule at days 0,7,21-30, followed by a booster at 12 months. 1

Standard Schedule (Preferred for Most Situations)

• Give three 1 mL doses at months 0,1, and 6 for routine immunization when there is no urgency for immediate protection 1
• This schedule provides 99% seroconversion for hepatitis A by month 2 and 84% protection against hepatitis B, with nearly 100% protection after the third dose 2
• Each dose contains 720 EL.U. of hepatitis A antigen and 20 μg of hepatitis B surface antigen 1

Accelerated Schedule (For Rapid Protection)

• Use the 4-dose accelerated regimen (days 0,7,21-30, plus month 12) when patients need protection before travel or imminent exposure 1
• This schedule is specifically designed for travelers departing to endemic regions within 1 month 3
• The accelerated regimen provides similar immunogenicity to monovalent vaccines given concurrently 3
• The standard 4-day grace period does NOT apply to the first 3 doses of the accelerated schedule due to its unique timing 1

Critical Timing Requirements

Minimum Intervals for Standard Schedule

• Minimum 4 weeks between doses 1 and 2 1
• Minimum 8 weeks between doses 2 and 3 1
• Minimum 16 weeks between doses 1 and 3 1

If Schedule is Interrupted

• Never restart the series—simply continue where you left off 1, 4
• Give the next dose as soon as possible while respecting minimum intervals 4
• Doses given ≤4 days before the minimum interval are considered valid for the standard schedule 1

Administration Details

• Inject intramuscularly into the deltoid muscle using a needle length appropriate for the patient's size 1
• Store at 35.6°F-46.4°F (2°C-8°C); do not freeze 1
• Each 1 mL dose is administered from a single-dose vial or prefilled syringe 1

Special Population Considerations

Pregnancy

• Twinrix is safe to use in pregnant women who need both hepatitis A and B protection 1
• This is in contrast to Heplisav-B and PreHevbrio, which lack sufficient pregnancy safety data 1

Hemodialysis and Immunocompromised Patients

• Do not use Twinrix in hemodialysis patients—they require higher-dose single-antigen hepatitis B vaccines (40 μg) 1
• Heplisav-B and PreHevbrio safety has not been established in hemodialysis patients 1

Age Restrictions

• Twinrix is licensed only for adults ≥18 years 1
• For adolescents 11-17 years requiring both vaccines, use separate monovalent vaccines 1

Expected Immune Response

• After 2 doses (month 2): >99% anti-HAV positive, 84% anti-HBs protected 2
• After 3 doses (month 7): 100% anti-HAV positive, 97.6-100% anti-HBs protected 5, 2
• Long-term follow-up shows 100% maintain anti-HAV and >95% maintain anti-HBs at 48 months 2

Common Pitfalls to Avoid

• Do not use Twinrix for hepatitis B vaccination alone—it unnecessarily exposes patients to hepatitis A antigen when not indicated 6
• Do not restart the series if interrupted—this wastes doses and delays protection 1, 4
• Do not give dose 3 before 16 weeks from dose 1, even if 8 weeks have passed since dose 2 1
• Do not apply the 4-day grace period to the accelerated schedule's first 3 doses 1
• Do not use in hemodialysis patients—they need higher-dose single-antigen hepatitis B vaccines 1

When to Choose Twinrix Over Single-Antigen Vaccines

• Use Twinrix when patients need protection against BOTH hepatitis A and B 6
• Specific indications include: international travelers to endemic regions, men who have sex with men at risk for both infections, persons with chronic liver disease requiring both vaccines 6
• Use single-antigen hepatitis B vaccine when only hepatitis B protection is needed 6