Hepatitis A vaccination

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Hepatitis A vaccination schedule indications immunogenicity

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Hepatitis A vaccine contraindications special populations post-exposure prophylaxis

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Hepatitis A Vaccination

Overview

Hepatitis A virus (HAV) infection is a self-limited but potentially severe acute hepatitis, preventable through highly effective vaccination. Two doses of HAV vaccine provide long-lasting (likely lifelong) protection.

Available Vaccines

Vaccine	Type	Doses
Havrix (GSK)	Inactivated HAV	2-dose series
Vaqta (Merck)	Inactivated HAV	2-dose series
Twinrix (GSK)	Combined HAV + HBV	3-dose series (or 4-dose accelerated)

Recommended Schedule

Children (Routine Immunization)

2-dose series beginning at 12 months of age
Second dose given 6–18 months after the first
This 2-dose series forms the universal childhood recommendation

Adults

2-dose series: doses separated by 6–12 months
No maximum age limit — any nonimmune adult at risk or who desires protection should receive it

Special Circumstance: Infants 6–11 months traveling internationally

Vaccine is recommended for preexposure prophylaxis before travel to HAV-endemic areas
This travel dose does not count toward the routine 2-dose childhood series (which restarts at 12 months) (Harrison's, p. 9422)

Indications

Routine

All children at age 12 months (universal childhood immunization)
Unvaccinated persons ≥2 years who want protection

High-Risk Groups

Travelers to countries with high HAV endemicity
Men who have sex with men (MSM) and bisexual men
Transgender persons
People who inject drugs (PWID)
Persons experiencing homelessness or prior incarceration
Chronic liver disease (hepatitis B, hepatitis C, alcoholic liver disease, cirrhosis)
Clotting factor disorders (e.g., hemophilia)
HIV-positive individuals (especially those with the above risk factors) (Primary Care Guidance for Persons with HIV, p. 25)
Close household/sexual contacts of adopted children from endemic countries
Food handlers (per local public health guidance)

Post-Exposure Prophylaxis (PEP)

Vaccine is now preferred over immune globulin (IG) for all persons ≥12 months exposed to HAV
For adults >40 years, IG (0.1 mL/kg) may be added to vaccination depending on individual risk assessment
For persons with contraindications to vaccination or infants <12 months: IG is used instead of or in addition to vaccine
Best administered within 2 weeks of exposure (Harrison's, p. 9422)

Immunogenicity

Seroconversion rates after 2 doses: >95–99% in immunocompetent individuals
HIV-positive patients have reduced immunogenicity; post-vaccination HAV IgG antibody testing should be repeated 1–2 months after the second dose. A repeat series is recommended if the patient remains seronegative (Primary Care Guidance for Persons with HIV, p. 25)
Protection is estimated to last ≥25 years (possibly lifelong) based on kinetic modeling

Contraindications & Precautions

Situation	Recommendation
Severe allergic reaction (anaphylaxis) to prior HAV vaccine dose or vaccine component	Contraindicated
Moderate to severe acute illness	Defer until recovery
Pregnancy	Vaccine is inactivated and considered safe; use if benefit outweighs theoretical risk
Immunocompromised	Vaccinate (may have reduced response); use IG if contraindicated

Pre-Travel Considerations

Single dose given at least 2 weeks before travel provides adequate protection in immunocompetent travelers
If departing <2 weeks before travel and age >40, immunocompromised, or have chronic liver disease — consider adding IG for immediate passive protection alongside the vaccine
Complete the 2-dose series on return for long-term protection

Key takeaway: Hepatitis A vaccine is safe, highly immunogenic, and recommended universally in children and in at-risk adults. Post-exposure use of vaccine (rather than IG) is now standard for most individuals ≥12 months of age.

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