Hepatitis A Post‑Exposure Prophylaxis (CDC Guidelines)

1. Primary Recommendation by Age and Health Status

• Healthy individuals 12 months – 40 years: give a single‑antigen hepatitis A vaccine (age‑appropriate dose) as soon as possible, ideally within 14 days of exposure. [CDC MMWR 2007] 1
• Persons > 40 years, immunocompromised, chronic liver disease, infants < 12 months, or pregnant women with vaccine contraindication: give immune globulin (IG) 0.02 mL/kg intramuscularly; vaccine may be used for those > 40 years only if IG is unavailable. [CDC MMWR 2007] 2

2. Age‑Stratified Approach

2.1 Ages 12 months – 40 years (Healthy)

• Single‑antigen hepatitis A vaccine is the preferred prophylaxis because it provides long‑term protection and is easy to administer. [CDC MMWR 2007] 1

2.2 Ages > 40 years

• IG 0.02 mL/kg is preferred owing to lack of efficacy data for vaccine in this group and higher risk of severe disease. [CDC MMWR 2007] 2
• Vaccine may be used when IG cannot be obtained, provided it is given within 14 days of exposure. [CDC MMWR 2007] 1
• Case‑fatality rate reaches 1.8 % in persons > 60 years, underscoring the need for prompt prophylaxis. [CDC MMWR 2007] 2

2.3 Infants < 12 months

• Administer IG 0.02 mL/kg alone because hepatitis A vaccine is not licensed for this age group. [CDC MMWR 2007] 1

3. Special Populations Requiring IG (with or without Vaccine)

• Immunocompromised patients: IG is essential because vaccine performance is unknown; vaccine may be added at a separate site for long‑term protection. [CDC MMWR 2007] 1
• Chronic liver disease: IG 0.02 mL/kg is recommended due to increased risk of fulminant hepatitis A; vaccine may be given simultaneously at a different site for future protection. [CDC MMWR 2007] 2
• Severe vaccine allergy: IG 0.02 mL/kg is the sole prophylactic agent. [CDC MMWR 2006] 3

4. Exposure‑Specific Recommendations

4.1 Close Personal / Household Contacts

• Provide prophylaxis (vaccine or IG as appropriate) to all previously unvaccinated household and sexual contacts of a confirmed case. [CDC MMWR 2007] 1
• For contacts who share illicit drugs with the case, give both IG and vaccine simultaneously at separate anatomic sites. [CDC MMWR 2006] 3
• Consider prophylaxis for other ongoing close contacts (e.g., regular babysitting). [CDC MMWR 2006] 3

4.2 Child‑Care Centers

• Offer prophylaxis to all unvaccinated staff and attendees when a case occurs in a child, employee, or in two or more households of attendees. [CDC MMWR 2006] 3
• If the center has no diaper‑wearing children, limit prophylaxis to classroom contacts of the index patient. [CDC MMWR 2006] 3
• In outbreaks involving ≥ 3 families, extend prophylaxis to household members of children who wear diapers. [CDC MMWR 2006] 3

4.3 Food‑Handler Exposure

• Give prophylaxis to other food handlers at the same establishment. [CDC MMWR 2006] 3
• Patrons generally do not need prophylaxis, but it may be considered when: (1) the infected food handler handled uncooked or cooked foods while infectious and had diarrhea or poor hygiene, and (2) patrons can be identified and treated within 2 weeks. [CDC MMWR 2006] 3
• Transmission from infected food handlers to patrons is usually low; most infected handlers do not transmit HAV. [CDC MMWR 2007] 2

4.4 Schools, Hospitals, Work Settings

• Routine prophylaxis is not indicated for a single case in elementary/secondary schools or office environments. [CDC MMWR 2007] 1

5. Critical Timing and Administration Details

• Prophylaxis must be given within 14 days of exposure for any proven efficacy; earlier administration yields better protection, and no data support effectiveness beyond two weeks. [CDC MMWR 2007] 2
• Do not wait for serologic confirmation of the index case before treating contacts, as delays jeopardize the time‑sensitive window. [CDC MMWR 2006] 3
• Do not use combination hepatitis A/B vaccine for post‑exposure prophylaxis because it contains only half the HAV antigen concentration and lacks efficacy data. [CDC MMWR 2007] 1

6. Dosing

When both IG and vaccine are indicated, administer them *simultaneously at separate anatomic sites*. [CDC MMWR 2006] 3

7. Common Pitfalls to Avoid

• Never delay prophylaxis to screen contacts for immunity. [CDC MMWR 2006] 3
• Never use combination hepatitis A/B vaccine for post‑exposure prophylaxis. [CDC MMWR 2007] 2
• Do not provide prophylaxis after the 2‑week window in common‑source outbreaks; effectiveness is lost. [CDC MMWR 2006] 3

8. Risk Magnitude Considerations

• Household secondary attack rates without prophylaxis range from 15 %–30 %, with higher transmission from infected young children. [CDC MMWR 2007] 2
• Restaurant patron attack rates after exposure to an infected food handler are generally low. [CDC MMWR 2007] 2
• The estimated magnitude of transmission risk should guide the choice between vaccine and IG when both are viable options. [CDC MMWR 2007] 1

Post-Exposure Prophylaxis for Hepatitis A

Primary Recommendation by Age and Risk Group

• The Centers for Disease Control and Prevention recommends that 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 4, 5
• For persons aged ≥12 months, single-antigen hepatitis A vaccine at age-appropriate dose is the preferred post-exposure prophylaxis, and timing is critical, with administration as soon as possible after exposure, within 14 days maximum for effectiveness 4, 5, 6
• No efficacy data exists for prophylaxis given >2 weeks after exposure, emphasizing the importance of prompt action 7, 8

Specific Exposure Settings Requiring Prophylaxis

• All previously unvaccinated household and sexual contacts of persons with serologically confirmed hepatitis A require prophylaxis, according to the Centers for Disease Control and Prevention 7, 8, 9
• Persons who shared illicit drugs with infected individual should receive both IG and hepatitis A vaccine simultaneously at separate anatomic sites 7, 8, 9
• The Advisory Committee on Immunization Practices recommends that prophylaxis is indicated in child care centers when one or more cases are recognized in children or employees, or when cases occur in two or more households of center attendees 7, 10

Administration Details

• The Centers for Disease Control and Prevention recommends using single-antigen hepatitis A vaccine only for post-exposure prophylaxis, not combination hepatitis A/B vaccine, which contains half the HAV antigen 7, 8, 11
• Complete the 2-dose series, with the second dose given 6-12 months later per licensed schedule for long-term protection, as advised by the Advisory Committee on Immunization Practices 7, 8
• Simultaneous administration of vaccine and IG at separate anatomic sites is recommended when both are indicated 7, 8

Critical Pitfalls to Avoid

• The Centers for Disease Control and Prevention advises never waiting for serologic confirmation before giving prophylaxis, as the 2-week window is critical, and never screening contacts for immunity before administering prophylaxis, as this causes harmful delays 7, 9
• Administer prophylaxis immediately based on clinical suspicion of exposure, and never use hepatitis A/B combination vaccine for post-exposure prophylaxis, as no efficacy data exists and antigen concentration is insufficient 7, 8, 11, 9