When should the hepatitis A (Hep A) vaccine be administered?

Hepatitis A Vaccine Administration Guidelines

The hepatitis A vaccine should be administered to all susceptible persons as soon as travel to high or intermediate endemic areas is considered, with specific timing and dosing based on age, health status, and travel circumstances.

Age-Based Recommendations

Infants (<12 months)

• Infants <6 months: No vaccine (not approved); use immune globulin (IG) 0.1-0.2 mL/kg 1

  • 0.1 mL/kg for travel up to 1 month
  • 0.2 mL/kg for travel up to 2 months
  • 0.2 mL/kg every 2 months for longer travel

• Infants 6-11 months: Single dose of hepatitis A vaccine when traveling to endemic areas 1

  • This dose does not count toward the routine 2-dose series
  • Begin routine series at 12 months of age

Children and Adults

• Children 12 months-40 years: Single dose as soon as travel is considered 1

  • Complete 2-dose series according to routine schedule (second dose 6-12 months later)

• Adults >40 years: Single dose as soon as travel is considered 1

  • May also receive IG (0.1-0.2 mL/kg) based on provider's risk assessment
  • Complete 2-dose series according to routine schedule

Special Populations

Immunocompromised Persons and Those with Chronic Liver Disease

• Single dose of hepatitis A vaccine 1
• Should also receive IG (0.1-0.2 mL/kg) at a separate anatomic site 1
• Complete vaccination series according to routine schedule

Persons with Vaccine Contraindications

• IG only (0.1 mL/kg) for postexposure prophylaxis 1
• For travel: 0.1-0.2 mL/kg based on duration of travel 1

Postexposure Prophylaxis

For unvaccinated persons exposed to hepatitis A:

• <12 months: IG only (0.1 mL/kg) 1
• 12-40 years: Single dose of hepatitis A vaccine 1
• >40 years: Single dose of hepatitis A vaccine; consider IG (0.1 mL/kg) based on risk assessment 1
• Immunocompromised/chronic liver disease: Both vaccine and IG (0.1 mL/kg) at separate anatomic sites 1

Timing Considerations

• Administer first dose as soon as travel is considered 1
• For optimal protection, vaccine should be given ≥2 weeks before expected exposure 2
• Postexposure prophylaxis should be given within 2 weeks of exposure 1

Dosage Information

• Children and adolescents: 0.5 mL per dose 2
• Adults: 1.0 mL per dose 2
• Administered by intramuscular injection 2

Key Clinical Considerations

• Hepatitis A vaccines are highly immunogenic with >95% of immunocompetent adults developing protective antibodies within 4 weeks of a single dose 3
• The second dose is primarily to ensure long-term immunity rather than immediate protection 1
• Older adults and those with chronic liver disease are at higher risk for severe hepatitis A disease, with case-fatality rates of approximately 1.8% among adults >60 years 1, 4
• Travelers to Australia, Canada, Western Europe, Japan, or New Zealand are at no greater risk than those in the United States 1

Common Pitfalls to Avoid

1. Delaying vaccination: Don't wait until just before travel - administer as soon as travel is considered
2. Missing high-risk groups: Ensure vaccination for all susceptible travelers to endemic areas, persons with chronic liver disease, men who have sex with men, drug users, and persons experiencing homelessness 3
3. Forgetting IG for special populations: Immunocompromised persons and those >40 years may need both vaccine and IG
4. Counting early infant doses: The travel dose for infants 6-11 months does not count toward the routine 2-dose series

Hepatitis A vaccination provides long-term protection, with vaccine-induced antibodies conferring protection for many years, possibly lifelong in most individuals 5.