El Tigre Journeys
in the heart of the Amazon

Health and Wellness
for travelers to the Peruvian Amazon
From the CDC Travel Page
Division of Quarantine, National Center for Infectious Diseases
Centers for Disease Control and Prevention, Atlanta, Georgia U.S.A.
updated October 10, 2001

Hepatitis, Viral, Type A
Health Information for International Travel, 2001–2002

Description
Hepatitis A is an enterically transmitted viral disease that causes fever, malaise, anorexia, nausea, and abdominal discomfort, followed within a few days by jaundice. The disease ranges in clinical severity from no symptoms to a mild illness lasting 1 to 2 weeks to a severely disabling disease lasting several months. In developing countries, hepatitis A virus (HAV) is usually acquired during childhood, most frequently as an asymptomatic or mild infection. Transmission can occur by direct person-to-person contact; through exposure to contaminated water, ice, or shellfish harvested from sewage-contaminated water; or from fruits, vegetables, or other foods that are eaten uncooked, and which can become contaminated during harvesting or subsequent handling.

Occurrence
HAV is highly endemic throughout the developing world, but, in general, of low endemicity in developed countries (within developed countries there might be pockets of increased endemicity).

Risk for Travelers
The risk of acquiring HAV infection for U.S. residents traveling abroad varies with living conditions, length of stay, and the incidence of HAV in the area visited. HAV is the most common vaccine-preventable disease in travelers and HAV vaccine or immune globulin (IG), or both, is recommended for all susceptible people traveling to or working in countries with an intermediate or a high endemicity of infection (see map below). Travelers to North America (except Mexico), Japan, Australia, New Zealand, and developed countries in Europe are at no greater risk of infection than in the United States. 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 areas, or frequently eat or drink in settings of poor sanitation. Nevertheless, many cases of travel-related HAV occur in travelers to developing countries with “standard” tourist itineraries, accommodations, and food consumption behaviors.

Preventive Measures

Vaccine
Two HAV vaccines are currently licensed in the United States: HAVRIX® (manufactured by GlaxoSmithKline) and VAQTA® (manufactured by Merck & Co., Inc). Both vaccines are made of inactivated virus adsorbed to aluminum hydroxide as an adjuvant. HAVRIX® is prepared with 2-phenoxyethanol as a preservative, while VAQTA® is formulated without a preservative. The vaccine should be administered by intramuscular injection in the deltoid muscle.

Both HAVRIX® and VAQTA® are currently licensed in two formulations, and the formulation and number of doses vary according to the recipient’s age. For HAVRIX®, the schedule for anyone 2 through 18 years of age is two 720-enzyme-linked immunosorbent assay unit (EL.U.) doses, with the second dose given 6 to 12 months after the first. For anyone 19 years of age or older, the schedule is two 1,400-EL.U. doses, with the second dose given 6 to 12 months after the first (see Table 1). For VAQTA®, the schedule for anyone 2 through 18 years of age is two 25-unit (U) doses, the second given 6 to 18 months after the first, and for anyone 19 years of age or older, the schedule is two 50-U doses given 6 months apart (see Table 2).

Vaccination with the age-appropriate dose (see Table 1 and Table 2) is preferred for anyone who plans to travel repeatedly or reside for long periods in high- or intermediate-risk areas. Studies have shown that protective antibody levels develop in 94% to 100% of those 19 years of age or older one month after the first dose of vaccine is given and protection can be assumed 4 weeks after receiving the first vaccine dose, although a second dose is necessary for long-term protection. Because protection might not be complete until 4 weeks after vaccine administration, anyone traveling to a high-risk area less than 4 weeks after the initial dose should also be given IG (0.02 milliliters per kilogram [mL/kg]) when available, but at a different injection site. Data on the long-term persistence of antibody after HAV vaccination are limited because the currently available vaccines have been under evaluation for only 5 to 7 years. Estimates of antibody persistence derived from kinetic models of antibody decline suggest that protective levels of anti-HAV could persist for at least 20 years.

Travelers younger than 2 years of age should receive a single dose of IG (0.02 mL/kg) because neither vaccine is licensed for infants. 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), which provides effective protection against HAV for up to 3 months. For anyone traveling for longer than 3 months, an IG dose of 0.06 mL/kg should be given, and must be repeated if the duration of travel is longer than 5 months. (See Table 3 for approximate IG dosages.)

Although vaccination of an immune traveler is not contraindicated and does not increase the risk of adverse effects, screening for total antibodies to HAV (anti-HAV) before travel can be useful to determine susceptibility and eliminate unnecessary vaccination or IG prophylaxis of immune travelers. Such serologic screening for susceptibility might be indicated for adult travelers who are likely to have had prior HAV infection if the cost of screening (laboratory and office visit) is less than the cost of vaccination or IG prophylaxis and if testing will not interfere with subsequent receipt of vaccine or IG. Such travelers can include those older than 40 years of age and those born in parts of the world with intermediate or high endemicity (see map). Postvaccination testing for serologic response is not indicated.

Adverse Reactions
Among those 19 years of age or older, the most frequently reported side effects occurring within 3 days following a dose of HAVRIX® were soreness at the injection site (56%), headache (14%), and malaise (7%). In clinical studies among those 18 years of age or younger, the most frequently reported side effects were soreness at the injection site (15%), feeding problems (8%), headache (4%), and injection-site induration (4%). Among those 19 years of age or older, the most frequent side effects occurring within 5 days following vaccination with VAQTA® were tenderness (53%), pain (51%), warmth at the injection site (17.3%), and headache (16.1%). Among those 18 years of age or younger, the most common side effects reported were pain (19%), tenderness (17%), and warmth at the injection site (9%).

Postlicensure reports, without regard to causality, of serious events received by the vaccine manufacturers have included (but might not have been limited to) anaphylaxis, Guillain-Barré syndrome, brachial plexus neuropathy, transverse myelitis, multiple sclerosis, encephalopathy, and erythema multiforme. Most of these events have occurred among adults, and many have occurred among people receiving other vaccines concurrently. For serious adverse events for which background incidence data were known, the rates for vaccine recipients were not higher than would be expected for an unvaccinated population.

Immune Globulin.  Immune globulin for intramuscular administration prepared in the United States has few side effects (primarily soreness at the injection site) and has never been shown to transmit infectious agents (hepatitis B virus [HBV], hepatitis C virus [HCV], or human immunodeficiency virus [HIV]). Since December 1994, all IG products commercially available in the United States have had to undergo a viral inactivation procedure or be negative for HCV ribonucleic acid (RNA) before release.

Precautions and Contraindications
Neither vaccine should be administered to travelers with a history of hypersensitivity to alum and HAVRIX® should not be administered to travelers with a history of hypersensitivity reactions to the preservative 2-phenoxyethanol. Because the vaccine is inactivated, no special precautions need to be taken for vaccination of immunocompromised travelers.

Pregnancy.—The safety of HAV vaccine for pregnant women has not been determined. However, because HAV vaccine is produced from inactivated HAV, the theoretical risk to either the pregnant woman or the developing fetus is thought to be very low. The risk of vaccination should be weighed against the risk of HAV in women travelers who might be at high risk for exposure to HAV. Pregnancy is not a contraindication to using immune globulin.

Other
HAV is inactivated by boiling or cooking food and beverage items to 85° Celsius (185° Fahrenheit) for at least one minute. Foods and beverages heated to this temperature and for this length of time cannot serve as vehicles for disease unless contaminated after heating. Adequate chlorination of water as recommended in the United States will inactivate HAV. Travelers should be advised that, to minimize their risk of HAV and other enteric diseases in developing countries, they should avoid potentially contaminated water or food. Travelers should also be advised to avoid drinking beverages (with or without ice) of unknown purity, and eating uncooked shellfish and uncooked fruits or vegetables that are not peeled or prepared by the traveler personally.

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