Hepatitis A is now a vaccine-preventable disease. Hepatitis A virus infection is primarily transmitted by the fecal-oral route. The average incubation period of 28 days is followed by symptomatic or asymptomatic disease. In children younger than six years, most infections (70 percent) are asymptomatic or occur with nonspecific symptoms. In older children and adults, infection is usually symptomatic, with jaundice occurring in 70 percent of adult patients. There is no chronic or carrier state. Bell discusses the usefulness of hepatitis A vaccine among children.
The highest disease incidence rates occur among children five to 14 years of age, with almost 30 percent of reported cases occurring among children younger than 15 years. Incidence rates are higher in the West and the Southwest than in the rest of the United States. The most common source of infection is household or sexual contact with a person who is infected with hepatitis A However, 40 to 50 percent of reported cases do not have an identified source.
Inactivated and live, attenuated hepatitis A vaccines have been developed, but only inactivated vaccines have been found to be efficacious and are labeled by the U.S. Food and Drug Administration for use in all persons at least two years of age. The two labeled vaccines, HAVRIX and VAQTA, are highly immunogenic, with more than 97 percent of adults and children at least two years of age developing protective levels of antibody by four weeks after one dose. Large boosts in antibody levels occur following a second dose given at least six months after the initial dose. The second dose is considered necessary for long-term protection. The duration of protection in adults is at least six years and probably significantly longer. Less data are available on the duration of protection in children. Limited data indicate that hepatitis A vaccine can be given concurrently with vaccines commonly given to overseas travelers and with immune globulin (IG). Recommendations for groups of people who should receive routine pre-exposure vaccinations are given in the accompanying table.
|Children living in communities with consistently elevated rates||Includes Alaska, Arizona, California, Idaho, Nevada, New Mexico, Oklahoma, Oregon, South Dakota, Utah, Washington and selected areas in other states†‡|
|International travelers§||Immune globulin may be given in addition to or instead of vaccine; children younger than two years should receive immune globulin|
|Men who have sex with men‖||Increased risk of fulminant hepatitis A with hepatitis A virus infection|
|Illicit drug users‖|
|Persons with chronic liver disease|
|Person receiving clotting factor concentrates|
|Persons who work with hepatitis A virus in research laboratory settings|
Hepatitis A vaccines are not recommended for postexposure prophylaxis because no trials have compared its use with IG, and IG administered within two weeks of exposure is highly efficacious. The most common adverse effect of hepatitis A vaccination is soreness at the injection site. There have been no serious adverse events among children or adults. The author concludes that routine vaccination is recommended in geographic areas in which incidence rates of hepatitis A have been consistently elevated. Children traveling to developing countries are another group recommended to receive vaccination. Pre- and post-vaccination testing is not indicated because of the low prevalence of infection among children and the high rate of vaccine response. The vaccine can be given at the same time as IG. The ultimate elimination of hepatitis A virus transmission will require vaccination of all children in the United States.