Vaccine Preventable Diseases

Hepatitis A

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Advisory Committee on Immunization Practices (ACIP) Recommendations

Infants
- All infants without contraindications should receive two doses of hepatitis A vaccine (trade names: Havrix®, Vaqta®) between 12-23 months of age.
- Doses should be given at least 6 months apart.

Children, Adolescents and Adults
- Older children and adults without contraindications who are at increased risk of hepatitis A infection (such as international travelers to countries with high or intermediate endemnicity; men who have sex with men; illegal drug users; contacts of recent international adoptees from countries endemic with hepatitis A virus; persons working with hepatitis A-infected primates; and those with a clotting factor disorder) as well as persons at risk of severe complications from hepatitis A infection (such as those with chronic liver disease) should also be routinely vaccinated [1, 2].

For More Information
ACIP recommendations: https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/hepa.html
Immunization schedules: http://www.cdc.gov/vaccines/schedules/index.html
 

Disease 

Hepatitis A Virus (HAV) is a nonenveloped RNA picornavirus that enters the body through the mouth via the fecal-oral route of transmission and replicates in the liver. Infected persons excrete virus beginning 10-12 days after infection and continuing up to 3 weeks after appearance of symptoms. The incubation period of HAV ranges from 15 to 50 days. Common symptoms are generalizable to all acute viral hepatitis disease, such as fever, malaise, nausea, anorexia, jaundice and dark urine, and generally persist no more than 2 months, although relapses may occur. About 70% of infections in children under 6 years of age are asymptomatic. Rarely, infection results in fulminant hepatitis, a severe complication with mortality rates estimated to be up to 80% [1].

Vaccine

Hepatitis A vaccine is an aluminum hydroxide-adjuvanted formalin-inactivated whole virus vaccine. There are two hepatitis A vaccines used in the United States: Havrix®, which is prepared with the preservative 2-phenoxyethanol, and Vaqta®, which does not contain a preservative. These vaccines are available in pediatric and adult formulations. There is also a hepatitis A-hepatitis B combination vaccine (trade name: Twinrix®) that is approved for use in persons over 18 years of age with an indication for both hepatitis A and hepatitis B vaccine. This vaccine should be administered according to the recommended schedule for hepatitis B vaccine in this age group [1].

Vaccine Effectiveness: Hepatitis A vaccines are very immunogenic. Over 95% of adults and 97% of children and adolescents develop immunity within a month of the first dose of vaccine, and 96-100% of children and adults develop immunity after the second dose. In clinical trials, vaccine efficacy of Havrix was estimated to be 94% and Vaqta estimated to be 100% [1].

Vaccine Safety: Self-limited, minor local reactions such as pain, redness or swelling are reported in approximately 20-50% of vaccine recipients. Mild systemic reactions such as fatigue, malaise and low-grade fever are reported in less than 10%. Besides very rare occurrences of anaphylaxis, no serious adverse events have been shown to be caused by to hepatitis A vaccination. Severe allergic reaction (e.g. anaphylaxis) to a previous dose or vaccine component is a contraindication to further hepatitis A vaccination [1].

Contraindications and Precautions: Severe allergic reaction (e.g. anaphylaxis) to a previous dose or vaccine component is a contraindication to further vaccination with hepatitis A vaccine. Current moderate to severe acute illness is a precaution to any vaccination [1].

Considerations in Pregnancy: Hepatitis A vaccine is not routinely recommended in pregnancy. The safety of hepatitis A vaccination during pregnancy has not been determined; however, because hepatitis A is an inactivated vaccine, the theoretic risk to the developing fetus is expected to be low. Therefore, the risk associated with vaccination should be weighed against the risk for hepatitis A in pregnant women who might be at high risk for exposure to HAV [2].

References

1. Epidemiology and Prevention of Vaccine-Preventable Diseases. Washington D.C.: Centers for Disease Control and Prevention; 2015.
2. Fiore AE, Wasley A, Bell BP. Prevention of hepatitis A through active or passive immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recommendations and reports : Morbidity and mortality weekly report Recommendations and reports 2006;55:1-23.