What is the recommended immunization schedule for hepatitis A (infectious hepatitis) vaccine for individuals at risk of exposure, including travelers to endemic areas, food handlers, and those with a history of liver disease?

Hepatitis A Immunization Schedule

The standard hepatitis A vaccination schedule consists of a 2-dose series with the second dose administered at least 6 months after the first dose for long-term immunity. 1

Routine Vaccination Schedule

Standard 2-Dose Series

• First dose: Administer as soon as vaccination is indicated 1
• Second dose: Administer at least 6 months after the first dose (typically 6-12 months or 6-18 months depending on vaccine formulation) 1, 2
• Critical timing: The second dose should not be given sooner than 6 months after the first dose, regardless of exposure risk 1

Age-Specific Dosing

• Adults: 1.0 mL intramuscular dose for both doses 2
• Children 2-17 years: 0.5 mL intramuscular dose for both doses 2
• Infants 6-11 months (travel only): Single dose before travel, but this does not count toward the routine 2-dose series, which must be initiated at age 12 months 1

Special Populations

Travelers to Endemic Areas

• Healthy travelers aged 12 months to 40 years: Administer one dose before travel; complete the series with a second dose at least 6 months later 1, 3
• Travelers over age 40: Administer one dose before travel, with optional immune globulin (0.1-0.2 mL/kg) based on provider risk assessment 1, 3
• Infants 6-11 months traveling: Give one dose before travel, then restart the 2-dose series at age 12 months 1

Immunocompromised Patients and Those with Chronic Liver Disease

• Preexposure vaccination: Administer standard 2-dose series at 0 and ≥6 months, with consideration for immune globulin (0.1-0.2 mL/kg) based on provider risk assessment 1
• These patients are at higher risk for severe outcomes from hepatitis A infection, making completion of the full series particularly important 1

Food Handlers and Healthcare Workers

• Follow the standard 2-dose schedule (0 and ≥6 months) as these individuals are at increased occupational risk 1

Important Clinical Caveats

Delayed Second Dose

• If the second dose is delayed beyond 12-18 months, it should still be administered—do not restart the series 4
• Research demonstrates that boosters given 20-31 months after the primary dose remain highly immunogenic (GMT 1544 mIU/mL in those >2 years old) 4
• The key principle: complete the series regardless of delay; there is no need to restart 4

Previously Vaccinated Adults

• No booster doses are needed for immunocompetent adults who completed the 2-dose series, even decades later 3
• The CDC's Advisory Committee on Immunization Practices confirms that hepatitis A vaccination provides likely lifelong immunity after the 2-dose series 3

Documentation Uncertainty

• If vaccination records are unavailable, serologic testing for anti-HAV IgG can confirm immunity 3
• Revaccination of previously immune individuals is safe and causes no harm—when in doubt and travel is imminent, vaccinate 3

Common Pitfalls to Avoid

• Do not use combination hepatitis A/B vaccine for postexposure prophylaxis—only single-antigen hepatitis A vaccine is recommended for this indication 5
• Do not administer the second dose earlier than 6 months after the first dose, as this may compromise long-term immunity 1
• Do not count the travel dose given to infants 6-11 months toward the routine series; restart at age 12 months 1
• Do not delay vaccination in travelers waiting for the "perfect" 6-month interval—give the first dose immediately and complete the series later 1, 3