What type of Hepatitis A (Hep A) vaccine should be administered for the second dose?

Second Dose Hepatitis A Vaccine Recommendation

Administer the same hepatitis A vaccine brand (either Havrix or Vaqta) that was used for the first dose, given at least 6 months after the initial dose. 1

Timing of Second Dose

• The second dose must not be administered sooner than 6 months after the first dose, regardless of HAV exposure risk. 1

• For Havrix: The second dose should be given 6 to 12 months after the first dose 1, 2

• For Vaqta: The second dose can be administered 6 to 18 months after the first dose 1, 2, 3

Vaccine Interchangeability

• While using the same vaccine brand for both doses is preferable, the vaccines are interchangeable - the 2-dose series may be completed with either Havrix or Vaqta if the original vaccine is unavailable 1, 2

• Studies demonstrate that completing the series with a different brand (e.g., Havrix followed by Vaqta) produces similar immunogenicity and booster response rates of 80-86% 4

Dosing by Age

For children aged 12 months to 18 years:

• Havrix: 0.5 mL (720 ELISA units) 1, 5, 3
• Vaqta: 0.5 mL (25 units) 1, 3

For adults aged ≥19 years:

• Havrix: 1.0 mL (1440 ELISA units) 5, 3
• Vaqta: 1.0 mL (50 units) 3

Important Clinical Considerations

• If the vaccination schedule is interrupted, do not restart the series - simply administer the second dose when feasible, as long as at least 6 months have elapsed since the first dose 1, 2

• The second dose is NOT required for postexposure prophylaxis, but should still be completed for long-term immunity 1

• After the second dose, seroconversion rates approach 100% with geometric mean titers rising substantially (ranging from 2,495 to 5,925 mIU/mL depending on vaccine and age) 5, 6

• Administer intramuscularly with appropriate needle length based on patient age and size 1, 2