What is the post-exposure prophylaxis (PEP) for hepatitis A virus (HAV) in individuals, particularly children, who have been exposed to hepatitis A?

Post-Exposure Prophylaxis for Hepatitis A

Hepatitis A vaccine should be administered to all persons aged ≥12 months as soon as possible after exposure to hepatitis A virus, ideally within 2 weeks, with immune globulin (IG) reserved for specific high-risk populations. 1

Primary Recommendation by Age and Risk Group

Standard Approach for Most Exposed Individuals

• For persons aged ≥12 months: Single-antigen hepatitis A vaccine at age-appropriate dose is the preferred post-exposure prophylaxis 1
• Timing is critical: Administer as soon as possible after exposure, within 14 days maximum for effectiveness 1
• No efficacy data exists for prophylaxis given >2 weeks after exposure 1

Infants Under 12 Months

• Use IG (0.1 mL/kg) intramuscularly for infants <12 months, as hepatitis A vaccine is not licensed for this age group 1

Persons Over 40 Years

The 2018 ACIP guidelines represent a significant shift from earlier recommendations:

• Hepatitis A vaccine should be administered to all persons aged >40 years for post-exposure prophylaxis 1
• IG (0.1 mL/kg) may be added to vaccine based on provider's risk assessment, particularly for those at highest risk for severe disease 1
• This updates the 2007 guidance that preferred IG alone for persons >40 years 1

Rationale for the change: While immunogenicity studies show slightly lower early antibody responses in older adults, seroprotection rates equalize by 30 days post-vaccination, and vaccine offers long-term protection plus greater availability 2

Mandatory IG Populations (Regardless of Age)

IG (0.1 mL/kg) must be used instead of vaccine alone for: 1

• Immunocompromised persons
• Persons with chronic liver disease (at increased risk for fulminant hepatitis A with case-fatality rates up to 1.8% in older adults) 1
• Persons with vaccine contraindications

Specific Exposure Settings Requiring Prophylaxis

Close Personal Contact

• All previously unvaccinated household and sexual contacts of persons with serologically confirmed hepatitis A require prophylaxis 1, 3
• Persons who shared illicit drugs (injection or non-injection) with infected individual should receive both IG and hepatitis A vaccine simultaneously at separate anatomic sites 1, 3
• Regular babysitters and others with ongoing close contact should receive prophylaxis 1, 3

Child Care Centers

Prophylaxis is indicated when: 1

• One or more cases are recognized in children or employees
• Cases occur in two or more households of center attendees
• For centers without diaper-wearing children, prophylaxis only needed for classroom contacts
• When outbreak occurs (≥3 families affected), consider prophylaxis for household members of all diaper-wearing attendees

Food Handler Exposure

• All other food handlers at the same establishment must receive prophylaxis when one food handler is diagnosed 1, 3
• Patrons typically do NOT need prophylaxis unless ALL of the following criteria are met: 1, 3
  • Food handler directly handled uncooked foods or foods after cooking
  • Food handler had diarrhea or poor hygienic practices during infectious period
  • Patrons can be identified and treated within 2 weeks of exposure

Settings Where Prophylaxis is NOT Routinely Indicated

• Schools, offices, or work settings when source of infection is outside these settings 1
• Hospital staff after patient admission (emphasize hygiene instead) 1
• Healthcare workers unless epidemiologic investigation confirms transmission 1, 3

Administration Details

Vaccine Administration

• Use single-antigen hepatitis A vaccine only (not combination hepatitis A/B vaccine, which contains half the HAV antigen) 1
• Complete the 2-dose series: Second dose should be given 6-12 months later per licensed schedule for long-term protection 1
• Simultaneous administration: If IG is also indicated, administer vaccine and IG at separate anatomic sites 1

Immune Globulin Dosing

• Updated dosage: 0.1 mL/kg intramuscularly (updated from previous 0.02 mL/kg recommendation) 1
• Timing: Administer as soon as possible, ideally within 24 hours, acceptable up to 14 days 1

Critical Pitfalls to Avoid

Do NOT Delay Administration

• Never wait for serologic confirmation before giving prophylaxis—the 2-week window is critical 1, 3
• Do not screen contacts for immunity before administering prophylaxis, as this causes harmful delays 3
• Administer immediately based on clinical suspicion of exposure 1, 3

Do NOT Use Combination Vaccine

• Never use hepatitis A/B combination vaccine (Twinrix) for post-exposure prophylaxis—no efficacy data exists and antigen concentration is insufficient 1

Special Considerations for High-Risk Groups

• For persons >40 years with chronic liver disease: Strongly consider adding IG to vaccine given case-fatality rates reaching 1.8% in those >60 years and increased risk of fulminant hepatitis 1
• Risk assessment matters: In high-risk transmission settings (e.g., household contacts with secondary attack rates of 15-30%), consider more aggressive prophylaxis 1

Evidence Quality Note

The recommendation for vaccine use in persons >40 years is based on a 2007 randomized trial showing vaccine non-inferiority to IG (4.4% vs 3.3% infection rates), though the study enrolled primarily children and younger adults 4. Immunogenicity studies show adequate seroprotection by 30 days in older adults, supporting the 2018 guideline expansion 2. The practical advantages of vaccine (long-term protection, ease of administration, greater availability) drove the policy change despite limited direct efficacy data in the oldest age groups 1.