What are the indications, contraindications, and recommended dosing schedule for hepatitis A vaccination?

Hepatitis A Vaccination: Indications, Contraindications, and Dosing

Hepatitis A vaccine should be administered as a 2-dose series starting at age 12 months or older, with the second dose given at least 6 months after the first dose, and is indicated for routine childhood immunization, international travelers, high-risk groups, and postexposure prophylaxis in persons ≥12 months of age. 1

Standard Dosing Schedule

The complete vaccination series requires 2 doses separated by at least 6 months for long-term immunity. 1

• Vaqta (Merck): Adults receive 1.0 mL (50 U) intramuscularly initially, followed by a booster at 6-12 months; children 2-17 years receive 0.5 mL (25 U) with booster at 6-18 months 2
• Havrix (SmithKline Beecham): Adults receive 1.0 mL (1440 ELISA units) intramuscularly initially, followed by 1.0 mL booster at 6-12 months; children 2-18 years receive 0.5 mL (720 ELISA units) 2
• The second dose should not be administered sooner than 6 months after the first dose, regardless of HAV exposure risk 1
• Seroconversion rates exceed 95% in healthy children and adults 2

Primary Indications

Routine Vaccination

• All children starting at age 12 months 1
• Travelers to regions with intermediate to high endemic hepatitis A rates 2, 3

High-Risk Groups

• Homosexual males 2
• Users of illicit intravenous drugs 2
• Persons working directly with nonhuman primates or hepatitis A virus 2
• Patients older than 30 years with chronic liver disease 2
• Persons who have received or are awaiting liver transplant 2
• Children living in high-prevalence areas or communities with periodic outbreaks 3

Postexposure Prophylaxis (PEP)

Hepatitis A vaccine is the preferred agent for PEP in persons ≥12 months, administered within 2 weeks of exposure. 1

Age-Specific PEP Recommendations

• Infants <12 months: Immune globulin (IG) only at 0.1 mL/kg; vaccine contraindicated 1
• Ages 12 months-40 years (healthy): 1 dose of vaccine alone; no IG needed 1
• Ages >40 years (healthy): 1 dose of vaccine; IG (0.1 mL/kg) may be added based on provider's risk assessment 1
• Ages ≥12 months (immunocompromised or chronic liver disease): 1 dose of vaccine PLUS IG (0.1 mL/kg) administered simultaneously at different anatomic sites 1

A second dose is not required for PEP efficacy, but should be completed at least 6 months later for long-term immunity. 1

Preexposure Protection for International Travelers

Infants and Young Children

• Infants <6 months: IG only at 0.1-0.2 mL/kg (0.1 mL/kg for travel up to 1 month; 0.2 mL/kg for travel up to 2 months) 1
• Infants 6-11 months: 1 dose of vaccine (this dose does NOT count toward the routine 2-dose series, which must begin at age 12 months) 1
• Ages 12 months-40 years: 1 dose of vaccine; no IG needed 1

Adults and Special Populations

• Ages >40 years: 1 dose of vaccine; IG (0.1-0.2 mL/kg) may be added based on provider's risk assessment 1
• All ages (immunocompromised): 1 dose of vaccine PLUS IG (0.1-0.2 mL/kg) based on provider's risk assessment 1

For persons not previously vaccinated, administer the first dose as soon as travel is considered and complete the series according to the routine schedule. 1

Contraindications

The only absolute contraindication is a life-threatening allergic reaction to a previous dose of hepatitis A vaccine or severe allergy to any vaccine component. 1

• Persons with vaccine contraindications should receive IG (0.1 mL/kg) for PEP instead 1
• Both vaccines are safe for use in pregnancy 2

Critical Timing Considerations

Postexposure prophylaxis must be administered within 2 weeks of exposure to be effective. 1

Important caveat: MMR and varicella vaccines should not be administered for at least 3 months after receipt of IG, as IG can interfere with live virus vaccine immunogenicity 1

For infants 6-11 months traveling internationally, simultaneous administration of MMR and hepatitis A vaccines is recommended, avoiding the need for IG which would delay MMR vaccination. 1

Long-Term Protection

Protective antibody levels persist for at least 25 years after completion of the 2-dose series, with 78.7-81.4% maintaining protective levels at 25 years. 4

Two-dose schedules provide more robust long-term protection than single-dose programs, with antibody persistence documented for at least 15 years (≥90%) versus 10 years (≥74%) for single-dose schedules. 5