September 24, 1996

Mode of Transmission:
Hepatitis A is an enterically transmitted viral disease which is highly endemic throughout the developing world but of low endemicity in developed countries such as the United States (U.S.). In developing countries, hepatitis A virus (HAV) is usually acquired during childhood, most frequently as an asymptomatic or mild infection. Transmission may occur by direct person-to-person contact, from contaminated water, ice, or shellfish harvested from sewage-contaminated water; or from fruits, vegetables or other foods which are eaten uncooked, but which may become contaminated during handling. Hepatitis A virus is inactivated by boiling or cooking to 85° C (1 minute); cooked foods may serve as vehicles for disease if they are contaminated after cooking.

Risk:
The risk of hepatitis A for U.S. citizens traveling abroad varies with living conditions, length of stay, and the incidence of HAV infection in areas visited. In general, travelers to northern and western Europe, Japan, Australia, New Zealand and North America (except Mexico) are at no greater risk of infection than they would be in the U.S. Areas of the world with intermediate or high rates of hepatitis A do pose an increased risk for travelers. For travelers to developing countries, risk of infection increases with duration of travel and is highest for those who live in or visit rural areas, trek in back country, or frequently eat or drink in settings of poor sanitation. Recent studies have shown that many cases of travel-related hepatitis A occur in travelers with "standard" tourist itineraries, accommodations, and food and beverage consumption behaviors. In developing countries, travelers should minimize their exposure to hepatitis A and other enteric diseases by avoiding potentially contaminated water or food. Travelers should avoid drinking water (or beverages with ice) of unknown purity and eating uncooked shellfish or uncooked fruits or vegetables that are not peeled or prepared by the traveler.

Recommendations:
Hepatitis A vaccine or immune globulin (IG) is recommended for all susceptible travelers to or for persons working in countries with intermediate or high rates of HAV infection. Vaccination of children 2 years of age and older, adolescents and adults with the age-appropriate dose of hepatitis A vaccine is preferred for persons who plan to travel repeatedly or reside for long periods in intermediate or high risk areas. Because of the current IG shortage, vaccine is also preferred for travelers 2 years of age and older desiring only short-term protection.

Immune globulin is recommended for travelers less than 2 years of age.

Dosing Information:
There are two hepatitis A vaccines currently licensed in the United States: HAVRIX® (manufactured by SmithKline Beecham Biologicals), and VAQTA® (manufactured by Merck & Co., Inc.). Both are inactivated vaccines, adsorbed to aluminum hydroxide as an adjuvant. HAVRIX® contains 2-phenoxyethanol as a preservative.

The vaccine should be administered by intramuscular injection into the deltoid muscle. It is licensed in adult and pediatric formulations, with different dosages and administration schedules. For HAVRIX®, adults (> 18 years) should be given two 1440 Elisa Unit (EL.U.) doses with the second dose administered 6 to 12 months after the first dose. There are two dosage schedules for children and adolescents (ages 2-18): a) 2 doses of 720 EL.U.of HAVRIX® with the second dose administered 6 to 12 months after the first dose, and b) 3 doses of 360 EL.U. of HAVRIX® with the second dose administered one month after the first dose and the third dose administered 6 to 12 months after the first dose. For VAQTA®, adults (> 17 years) should be given two 50 unit (U) doses with the second dose administered 6 months later. The schedule for children and adolescents (ages 2-17) includes 2 doses of VAQTA® with the second dose administered 6 to 18 months after the first dose. Travelers can be considered to be protected four weeks after receiving the initial vaccine dose. Individuals who will travel to intermediate or high risk areas less than 4 weeks after the initial dose of vaccine should also be given IG (0.02 ml/kg of body weight). The vaccine series must be completed for long-term protection. Estimates derived from modeling techniques suggest that vaccine may provide protective antibody against hepatitis A for at least 20 years.

Travelers who are allergic to a vaccine component or otherwise elect not to receive vaccine should receive a single dose of IG (0.02 ml/kg of body weight) if travel is for less than 3 months. For prolonged travel or residence in developing countries, a higher dosage of IG should be used (0.06 ml/kg of body weight) and should be repeated every 5 months.

Prevaccination testing:
Prevaccination testing is not indicated for children because of their expected low prevalence of prior infection. For some adult travelers who are likely to have had hepatitis A in the past (i.e., persons older than 40 years of age, persons born in parts of the world with intermediate or high levels of hepatitis A, or persons with clotting disorders), screening for HAV antibodies (anti-HAV) before travel may be useful to determine susceptibility and eliminate unnecessary vaccination or IG prophylaxis. Factors to consider before doing prevaccination testing include: 1) the cost of vaccination compared with the cost of serologic testing, including the cost of an additional visit and 2) the likelihood that prevaccination testing will not interfere with completion of the vaccine series.

Safety:

Immune globulin
Intramuscular IG prepared in the United States has an excellent safety profile. IG produced in developing countries may not meet the standards for purity required in most developed countries. Persons needing repeat doses in other countries should use products that meet U.S. license requirements.

Hepatitis A Vaccine
Experience to date indicates that Hepatitis A vaccine has an excellent safety profile. Approximately 50,000 persons have received HAVRIX® in clinical studies. No serious adverse events have been observed which could be attributed definitively to hepatitis A vaccine. In combined clinical trials, 16,252 doses of VAQTA® were given to 9,191 healthy children, adolescents and adults. No serious vaccine-related adverse experiences were observed during clinical trials. For both vaccines, the most common side effects are mild problems that usually disappear within 1 to 2 days. These may include soreness or swelling at the site of injection, headache, tiredness and/or loss of appetite. As with any medication, there are very small risks that serious problems such as severe allergic reaction and even death could occur after getting the vaccine. Most people who have received hepatitis A vaccine have no problems from it.

Contraindications:

Immune globulin
Pregnancy is not a contraindication to the use of IG. Serious adverse events from IG are rare.

Hepatitis A vaccine
Hepatitis A vaccine should not be administered to persons with a history of hypersensitivity reactions to components in the vaccine (i.e., alum or the preservative 2-phenoxyethanol). Vaccination of an immune person is not contraindicated and does not increase the risk of adverse events. Because the vaccine is inactivated, no special precautions need to be taken in vaccination of immunocompromised persons. The theoretical risk to the developing fetus is expected to be low when vaccine is administered to pregnant women. No animal or human data exist from which to determine the safety of hepatitis A vaccination during pregnancy. The theoretical risk of vaccination should be weighed against the risk of hepatitis A in women who may be at high risk of exposure to HAV.

Division of Quarantine 
National Center for Infectious Diseases 
Centers for Disease Control and Prevention 
Atlanta, GA