What is the recommended dose and administration schedule for Twinrix (hepatitis A and B vaccine) in adults and children over 1 year of age?

Twinrix Dosing and Administration

Twinrix is administered as 1 mL intramuscularly 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, plus a booster at 12 months) for adults ≥18 years only. 1

Standard Dosing Schedule

• Give three 1 mL doses at months 0,1, and 6 for routine immunization when there is no urgency for immediate protection. 1, 2
• Each 1 mL dose contains 720 ELISA units (EL.U.) of hepatitis A antigen and 20 mcg of recombinant hepatitis B surface antigen protein. 3
• This is the most commonly used schedule and suits the majority of adult patients. 2
• After 3 doses, antibody responses to both antigens are equivalent to responses seen when single-antigen vaccines are administered separately on standard schedules. 3

Accelerated Schedule

• Use the 4-dose accelerated regimen (days 0,7,21-30, and 12 months) when patients need protection before travel or imminent exposure. 1, 2
• The third dose can be administered between 21 and 30 days after the first dose. 2
• The fourth dose at 12 months is essential for long-term protection and must not be forgotten. 2
• The standard 4-day grace period does not apply to the first 3 doses of the accelerated schedule. 1

Administration Technique

• Inject intramuscularly into the deltoid muscle using a needle length appropriate for the patient's age and size. 3, 1
• Shake the vaccine well before administration to obtain a slightly opaque white suspension. 2
• Each 1 mL dose is administered from a single-dose vial or prefilled syringe. 1

Storage Requirements

• Store at 35.6°F–46.4°F (2°C–8°C) and do not freeze. 3

Age Restrictions

• Twinrix is licensed only for adults ≥18 years. 3, 1, 2
• For children aged 1-18 years, use separate single-antigen hepatitis A and B vaccines instead. 3

Managing Interrupted Schedules

• If the vaccination schedule is interrupted, do not restart the series—simply continue where you left off and administer the next dose as soon as possible. 2
• There is no maximum interval between doses. 4
• Ensure at least 8 weeks between the second and third doses. 2

Special Populations

• Twinrix is safe to use in pregnant women who need both hepatitis A and B protection. 1, 4
• The vaccine can be used in immunodeficient individuals, as it is inactivated and has not shown increased safety risks. 2
• Do not use Twinrix in hemodialysis patients—they require higher-dose single-antigen hepatitis B vaccines (40 mcg formulations). 3, 1, 4

Critical Pitfalls to Avoid

• Do not use Twinrix for hepatitis B vaccination alone—it unnecessarily exposes patients to hepatitis A antigen when not indicated. 1
• Do not restart the series if interrupted—it wastes doses and delays protection. 1, 2
• 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. 3, 1

When to Choose Twinrix

• Use Twinrix when patients need protection against both hepatitis A and B. 1
• Use single-antigen hepatitis B vaccine when only hepatitis B protection is needed. 1