How Effective is Inactivated Hepatitis A Vaccine?

Patient Presentation
A mother of two school aged children called because she was worried that they had consumed contaminated strawberries at their elementary school in their school lunch. There had been a recent outbreak in another state of Hepatitis A contaminated strawberries. The strawberries had been mislabeled as being manufactured in the US when they had been produced in Mexico. The outbreak in the other state had caused 150 cases of Hepatitis A disease. In the mother’s state, the strawberries had been distributed to various schools but it was unclear if any had actually been served to students and there had been no reported disease cases. It was unclear if the patients had even eaten any strawberries of any type at their own school. The patients were asymptomatic, healthy and fully immunized.

The diagnosis of an unlikely exposure to Hepatitis A was made. The state Department of Health was recommending immunoglobulin only for specific high-risk populations at that time and these children were not high risk. Therefore there was nothing specific to do but to monitor the children. Since this time period, recommendations for post-exposure prophylaxis to Hepatitis A have changed to include active vaccination.

In 1997, 150 cases of Hepatitis A (HAV) were reported in Michigan from contaminated strawberries. The strawberries were produced in Mexico and distributed to the US Department of Agriculture sponsored school lunch programs in six states. Most of the containers were not served to students and the majority of cases occurred in Michigan only.

HAV is an RNA virus of the picornavirus family. The virus is spread mainly by fecal-oral contamination and contaminated food and water supplies. The incubation period is 15 to 50 days. The average is 28 days. Patients are most infectious during the one to two weeks before onset of jaundice or elevation of liver enzymes and risk of spread to others is minimal by one week after the onset of jaundice.

HAV is a self-limited illness whose symptoms usually include fever, jaundice, anorexia, nausea, and malaise. Risk factors include close personal contact or exposure to persons with HAV, child in a day care center where a case has been report, international adoptee, men who have sex with men, and use of illegal drugs and of course, food borne exposure. In approximately 2/3 of cases, the source cannot be determined.

In areas of the world where HAV is endemic, young children who acquire the disease early in life are usually asymptomatic. In areas of the world where the virus is not endemic, disease is acquired much later in life and is symptomatic. Endemicity rates are highly correlated to socioeconomic status and clean water supplies.

Because it can be difficult to distinguish HAV from other hepatitides, testing for anti-HAV is recommended. Anti-HAV IgM occurs without 2 weeks of infection and IgG occurs generally after that time.

Treatment is symptomatic with rest and good nutritional support. Fulminant hepatitis is rare but can require emergency liver transplantation. Post-exposure prophylaxis at the time of this case was to treat specific high-risk patients with immunoglobulin. Since that time the recommendations have changed and HAV vaccine is given to patients within one to two weeks of exposure. Benefit of HAV vaccine after this time has not been clearly determined. Since 2006, the United States universal HAV vaccination of the pediatric population has been recommended at after 12 months of age with 2 doses of inactivated vaccine.

Prior to licensing of the inactivated vaccine in 1995, approximately 100 deaths in the United States occurred per year because of Hepatitis A, but has markedly decreased since.

In areas of the world where HAV is endemic, HAV vaccination is usually not given because of the cost-benefit ratio. In areas where HAV is not endemic such as high socioeconomic countries, HAV vaccine is recommended. In mixed endemic areas, the vaccine is generally recommended, but cost may be a limiting factor in certain countries or circumstances globally.

Learning Point
HAV vaccine is highly immunogenic.
After the first vaccine, antibodies are detected by two weeks with 95% of healthy individuals having protective antibody concentrations at one month post-vaccination. After the second dose, 99-100% of patients have protective antibody concentrations. The protection duration is felt to be at least 15 years or more, and many scientists feel that the vaccination may offer lifetime community. The adverse effects are usually mild local pain or even less commonly, induration of the injection site.

Questions for Further Discussion
1. Is Hepatitis A vaccine given locally and why?
2. In an unimmunized individual who is traveling to an endemic area, when should Hepatitis A vaccine be given?
3. How are exposures of food handlers treated?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Hepatitis A

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Hepatitis A Associated with Consumption of Frozen Strawberries — Michigan, March 1997. MMWR. April 4, 1997. 46 (13);288, 295.

Jacobsen KH, Wiersma ST. Hepatitis A virus seroprevalence by age and world region, 1990 and 2005. Vaccine. 2010 Sep 24;28(41):6653-7.

Ott JJ, Irving G, Wiersma ST. Long-term protective effects of hepatitis A vaccines. A systematic review. Vaccine. 2012 Dec 17;31(1):3-11.

Matheny SC, Kingery JE. Hepatitis A. Am Fam Physician. 2012 Dec 1;86(11):1027-34; quiz 1010-2.

American Academy of Pediatrics. Hepatitis A, In Pickering LD, Baker CJ, Kimberlin DW, Long SS, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th edit. Elk Grove Village, IL: American Academy of Pediatrics; 2012;361-369.


Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital