After close personal or household exposure to hepatitis A, what is the recommended post‑exposure prophylaxis, including whether to use hepatitis A vaccine or hepatitis A immune globulin, timing (within 14 days), dosage, and special considerations for patients over 40 years, immunocompromised, chronic liver disease, pregnancy, or severe vaccine allergy?

Hepatitis A Post-Exposure Prophylaxis

Primary Recommendation

For healthy persons aged 12 months to 40 years, administer single-antigen hepatitis A vaccine alone as soon as possible within 14 days of exposure; for persons over 40 years, immunocompromised patients, those with chronic liver disease, infants under 12 months, or pregnant women with contraindications to vaccine, use immune globulin (IG) 0.02 mL/kg, though vaccine may be considered for those over 40 if IG is unavailable. 1

Age-Stratified Approach

Ages 12 Months to 40 Years (Healthy)

• Single-antigen hepatitis A vaccine at age-appropriate dose is the preferred prophylaxis because it provides long-term protection and ease of administration 1
• Administer one dose as soon as possible after exposure, ideally within 14 days 1, 2
• A randomized trial of 1,090 contacts aged 2-40 years demonstrated vaccine efficacy comparable to IG, with symptomatic infection rates of 4.4% for vaccine versus 3.3% for IG (relative risk 1.35,95% CI 0.70-2.67) 3
• Complete the two-dose series with the second dose at 6-12 months for long-term protection 2

Ages Over 40 Years

• IG 0.02 mL/kg is preferred due to absence of efficacy data for vaccine in this age group and increased risk of severe disease 1
• Vaccine may be used if IG cannot be obtained, but should be administered as soon as possible within 14 days 1
• Immunogenicity studies show delayed seroprotection in older adults, with lower proportions protected at 15 days post-vaccination compared to younger adults, though similar protection by 30 days 4
• The case-fatality rate reaches 1.8% in persons over 60 years, making prevention particularly critical 1

Infants Under 12 Months

• Administer IG 0.02 mL/kg alone, as vaccine is not licensed for this age group 1, 5

Special Populations Requiring IG (with or without vaccine)

Immunocompromised Patients

• Administer both hepatitis A vaccine and IG simultaneously at separate anatomic sites 5
• IG is essential because vaccine performance is unknown in immunocompromised hosts 1

Chronic Liver Disease

• Use IG 0.02 mL/kg because these patients are at increased risk for fulminant hepatitis A 1
• Vaccine may be given simultaneously at a separate site if long-term protection is also desired 1
• Fulminant hepatitis occurs more frequently in patients with underlying chronic liver disease 1

Pregnancy

• Vaccine is safe in pregnancy, but if contraindicated for other reasons, use IG 6
• Both vaccines (Havrix and Vaqta) are considered safe for pregnant women 6

Severe Vaccine Allergy

• Use IG 0.02 mL/kg as the sole prophylactic agent 1

Exposure-Specific Recommendations

Close Personal/Household Contact

• Administer prophylaxis to all previously unvaccinated household and sexual contacts of serologically confirmed hepatitis A cases 1, 2
• For persons who shared illicit drugs with infected individuals, administer both IG and vaccine simultaneously at separate anatomic sites 1, 2
• Consider prophylaxis for other ongoing close personal contacts (e.g., regular babysitting) 1

Child Care Centers

• Provide prophylaxis to all previously unvaccinated staff and attendees if one or more cases occur in children or employees, or if cases occur in two or more households of attendees 1, 2
• In centers without diaper-wearing children, prophylaxis need only be given to classroom contacts of the index patient 1
• When outbreaks occur (three or more families), consider prophylaxis for household members of children in diapers 1

Food Handler Exposure

• Administer prophylaxis to other food handlers at the same establishment 1
• For patrons, prophylaxis is typically not indicated but may be considered if: (1) the food handler directly handled uncooked or cooked foods while infectious AND had diarrhea or poor hygiene, AND (2) patrons can be identified and treated within 2 weeks 1
• Common-source transmission to patrons is generally low risk, as most infected food handlers do not transmit HAV 1

Schools, Hospitals, Work Settings

• Routine prophylaxis is not indicated for single cases in elementary/secondary schools or office settings 1

Critical Timing and Administration Details

Timing Window

• Prophylaxis must be administered within 14 days of exposure for any proven efficacy 1, 5, 2
• Earlier administration is better; no data support efficacy beyond 2 weeks 1, 5
• Do not wait for serologic confirmation of the index case before administering prophylaxis, as delays compromise effectiveness 2

Vaccine Formulation

• Use only single-antigen hepatitis A vaccine (Havrix or Vaqta) for post-exposure prophylaxis 5, 2
• Do not use combination hepatitis A/B vaccine, as it contains half the HAV antigen concentration and lacks efficacy data for post-exposure use 1, 5, 2

Dosing

• IG dose: 0.02 mL/kg intramuscularly 1
• Vaccine dose: Age-appropriate single dose (Vaqta: 25 U for children 2-17 years, 50 U for adults; Havrix: 720 ELISA units for ages 2-18 years, 1440 ELISA units for adults) 6
• When both IG and vaccine are indicated, administer simultaneously at separate anatomic sites 1, 5, 2

Common Pitfalls to Avoid

• Never delay prophylaxis to screen contacts for immunity, as this causes harmful delays beyond the 14-day window 1, 2
• Never use combination hepatitis A/B vaccine for post-exposure prophylaxis due to insufficient antigen concentration and lack of efficacy data 1, 5, 2
• Never wait for serologic confirmation of the index case before treating contacts, as the time-sensitive window is critical 2
• Do not provide prophylaxis after the 2-week window in common-source outbreaks once cases have begun to occur, as the effective period has passed 1

Risk Magnitude Considerations

• Secondary attack rates in households range from 15-30% without prophylaxis, with higher transmission from infected young children 1
• Attack rates among restaurant patrons exposed to infected food handlers are generally low 1
• The magnitude of transmission risk should inform decisions between vaccine and IG when both are options 1