The clinical case definition for acute viral hepatitis is 1) discrete onset of symptoms (e.g., nausea, anorexia, fever, malaise, or abdominal pain) and 2) jaundice or elevated serum aminotransferase levels. Because the clinical characteristics are the same for all types of acute viral hepatitis, hepatitis A diagnosis must be confirmed by a positive serologic test for immunoglobulin M (IgM) antibody to hepatitis A virus, or the case must meet the clinical case definition and occur in a person who has an epidemiologic link with a person who has laboratory-confirmed hepatitis A (i.e., household or sexual contact with an infected person during the 15–50 days before the onset of symptoms).

The case definition for acute hepatitis A is available at the following link:

    Acute Hepatitis A

Additional guidance on viral hepatitis surveillance and case management is available at http://www.cdc.gov/hepatitis/SurveillanceGuidelines.htm.

Hepatitis A rates in the United States have declined by 89% since hepatitis A vaccine first became available in 1995.

In 2006, 3,579 acute symptomatic cases of hepatitis A were reported; the incidence was 1.2/100,000, the lowest rate ever recorded. After adjusting for asymptomatic infection and underreporting, the estimated number of new infections was 32,000.

• Person-to-person transmission through the fecal-oral route (i.e., ingestion of something that has been contaminated with the feces of an infected person) is the primary means of HAV transmission in the United States. Most infections result from close personal contact with an infected household member or sex partner.
• Common-source outbreaks and sporadic cases also can occur from exposure to fecally contaminated food or water. Uncooked HAV-contaminated foods have been recognized as a source of outbreaks. Cooked foods also can transmit HAV if the temperature during food preparation is inadequate to kill the virus or if food is contaminated after cooking, as occurs in outbreaks associated with infected food handlers. Waterborne outbreaks are infrequent in developed countries with well-maintained sanitation and water supplies.

• Travelers to countries with high or intermediate endemicity of HAV infection
• Men who have sex with men
• Users of injection and non-injection illegal drugs
• Persons with clotting factor disorders
• Persons working with nonhuman primates susceptible to HAV infection

• Fever
• Fatigue
• Loss of appetite
• Nausea
• Vomiting
• Abdominal pain
• Dark urine
• Clay-colored bowel movements
• Joint pain
• Jaundice

In children aged <6 years, 70% of infections are asymptomatic; if illness does occur, it is typically not accompanied by jaundice. Among older children and adults, infection is typically symptomatic, with jaundice occurring in >70% of patients.

Symptoms usually last less than 2 months, although 10%–15% of symptomatic persons have prolonged or relapsing disease for up to 6 months.

The average incubation period for hepatitis A is 28 days (range: 15–50 days).

HAV can live outside the body for months, depending on the environmental conditions. The virus is killed by heating to 185 degrees F (85 degrees C) for one minute. However, the virus can still be spread from cooked food if it is contaminated after cooking. Adequate chlorination of water, as recommended in the United States, kills HAV that enters the water supply.

No. Hepatitis A does not become chronic.

No. IgG antibodies to HAV, which appear early in the course of infection, provide lifelong protection against the disease.

Vaccination with the full, two-dose series of hepatitis A vaccine is the best way to prevent HAV infection. Hepatitis A vaccine has been licensed in the United States for use in persons 12 months of age and older. The vaccine is recommended for persons who are more likely to get HAV infection or are more likely to get seriously ill if they get hepatitis A (see Who should be vaccinated against hepatitis A?).

Immune globulin is available for short-term protection (approximately 3 months) against hepatitis A, both pre- and post-exposure. Immune globulin must be administered within 2 weeks after exposure for maximum protection.

Good hygiene — including handwashing or use of hand sanitizer after using the bathroom, changing diapers, and before preparing or eating food — is also integral to hepatitis A prevention, given that the virus is transmitted through the fecal–oral route.

Hepatitis A vaccination is recommended for all children at age 1 year, for persons who are at increased risk for infection, for persons who are at increased risk for complications from hepatitis A, and for any person wishing to obtain immunity. The following groups are recommended to receive hepatitis A vaccination:

All children at age 1 year (i.e., 12–23 months).  Children who have not been vaccinated by age 2 can be vaccinated at subsequent visits.

Children and adolescents ages 2–18 who live in states or communities where routine hepatitis A vaccination has been implemented because of high disease incidence. Before 2006, when hepatitis A vaccination was first recommended for all children at age 1 year, vaccination had been targeted to children living in states or communities that had historically high rates of hepatitis A. States, counties, and communities with existing hepatitis A vaccination programs for children aged 2–18 years are encouraged to maintain these programs. In those communities, new efforts focused on routine vaccination of children at age 1 year should enhance, not replace, ongoing programs directed at a broader population of children.

Persons traveling to or working in countries that have high or intermediate rates of hepatitis A. Persons from developed countries who travel to developing countries are at high risk for hepatitis A. The risk for hepatitis A exists even for travelers to urban areas, those who stay in luxury hotels, and those who report that they have good hygiene and that they are careful about what they drink and eat (see Hepatitis A and International Travel for more information).

Men who have sex with men. Sexually active men (both adolescents and adults) who have sex with men should be vaccinated. Hepatitis A outbreaks among men who have sex with men have been reported frequently. Recent outbreaks have occurred in urban areas in the United States, Canada, and Australia.

Users of illegal injection and noninjection drugs. During the past two decades, outbreaks of hepatitis A have been reported with increasing frequency among users of both injection and noninjection drugs (e.g., methamphetamine) in North America, Europe, and Australia.

Persons who have occupational risk for infection. Persons who work with HAV-infected primates or with HAV in a research laboratory setting should be vaccinated. No other groups have been shown to be at increased risk for HAV infection because of occupational exposure.

Persons who have chronic liver disease. Persons with chronic liver disease who have never had hepatitis A should be vaccinated, as they have a higher rate of fulminant hepatitis A (i.e., rapid onset of liver failure, often leading to death). Persons who are either awaiting or have received liver transplants also should be vaccinated.

Persons who have clotting-factor disorders. Persons who have never had hepatitis A and who are administered clotting-factor concentrates, especially solvent detergent-treated preparations, should be vaccinated.

Two single-antigen hepatitis A vaccines, HAVRIX® (manufactured by GlaxoSmithKline) and VAQTA® (manufactured by Merck & Co., Inc), are currently licensed in the United States. A combination vaccine, TWINRIX® (manufactured by GlaxoSmithKline), contains both HAV (in a lower dosage; see table) and hepatitis B virus antigens. All are inactivated vaccines.

Licensed dosages and schedules for HAVRIX ® 1
Age	Dose (ELISA units)2	Volume (mL)	No. of doses	Schedule (mos)3
12 mos–18 yrs	720	0.5	2	0,6-12
≥19 years	1,440	1.0	2	0,6-12

¹Hepatitis A vaccine, inactivated, GlaxoSmithKline.
²Enzyme-linked immunosorbent assay units.
³0 months represents timing of the initial dose; subsequent numbers represent months after the initial dose.

Licensed dosages and schedules for VAQTA ® 1
Age	Dose (U.)2	Volume (mL)	No. of doses	Schedule (mos)3
12 mos–18 yrs	25	0.5	2	0,6-18
≥19 years	50	1.0	2	0,6-18

¹Hepatitis A vaccine, inactivated, Merck & Co., Inc.
²Units.
³0 months represents timing of the initial dose; subsequent numbers represent months after the initial dose.

Licensed dosages and schedules for TWINRIX ® 1
Age	Dose (ELISA units)2	Volume (mL)	No. of doses	Schedule
≥ 18 yrs	720	1.0	3	0, 1, 6 mos
≥ 18 yrs	720	1.0	4	0, 7, 21–30 days + 12 mos3

¹Combined hepatitis A and hepatitis B vaccine, inactivated, GlaxoSmithKline.
²Enzyme-linked immunosorbent assay units.
³This 4-dose schedule enables patients to receive 3 doses in 21 days; this schedule is used prior to planned exposure with short notice and requires a fourth dose at 12 months.

A recent review by an expert panel, which evaluated the projected duration of immunity from vaccination, concluded that protective levels of antibody to HAV could be present for at least 25 years in adults and at least 14–20 years in children.

Yes. Hepatitis B, diphtheria, poliovirus (oral and inactivated), tetanus, oral typhoid, cholera, Japanese encephalitis, rabies, and yellow fever vaccines and immune globulin can be given at the same time that hepatitis A vaccine is given, but at a different injection site.

Yes. Although studies have not been done to examine this issue, there is no reason to believe that using single-antigen vaccine from different manufacturers would be a problem.

The second dose should be administered as soon as possible. The first dose does not need to be readministered.

The safety of hepatitis A vaccination during pregnancy has not been determined; however, because the vaccine is produced from inactivated HAV, the theoretical risk to the developing fetus is expected to be low. The risk associated with vaccination, however, should be weighed against the risk for hepatitis A in women who might be at high risk for exposure to HAV.

Yes. Because hepatitis A vaccine is inactivated, no special precautions need to be taken when vaccinating immunocompromised persons.

No. If necessary, administering extra doses of hepatitis A or hepatitis B vaccine is not harmful.

• Persons who were born in geographic areas with high or intermediate prevalence of HAV infection
• Older adolescents and adults in certain population groups (i.e., American Indians, Alaska Natives, and Hispanics)
• Adults in groups that have a high prevalence of infection (e.g., injection drug users)

Prevaccination testing might also be warranted for all older adults. The decision to test should be based on 1) the expected prevalence of immunity, 2) the cost of vaccination compared with the cost of serologic testing, and 3) the likelihood that testing will not interfere with initiation of vaccination.

No. Postvaccination testing is not indicated because of the high rate of vaccine response among adults and children. In addition, not all testing methods approved for routine diagnostic use in the United States have the sensitivity to detect low, but protective, anti-HAV concentrations after vaccination.

Food service workers. Foodborne hepatitis A outbreaks are relatively uncommon in the United States; however, when they occur, intensive public health efforts are required for their control.

Although persons who work as food handlers have a critical role in common-source foodborne outbreaks, they are not at increased risk for hepatitis A because of their occupation. Consideration may be given to vaccination of employees who work in areas where community-wide outbreaks are occurring and where state and local health authorities or private employers determine that such vaccination is cost-effective.

Sewage workers. In the United States, no work-related outbreaks of hepatitis A have been reported among workers exposed to sewage.

Healthcare workers. Healthcare workers are not at increased risk for hepatitis A. If a patient with hepatitis A is admitted to the hospital, routine infection-control precautions will prevent transmission to hospital staff.

Children under 12 months of age. Because of the limited experience with hepatitis A vaccination among children in this age group, the vaccine is not currently licensed for children age <12 months.

Child care center attendees. The frequency of outbreaks of hepatitis A is not high enough in this setting to warrant routine hepatitis A vaccination. In some communities, however, child care centers play a role in sustaining community-wide outbreaks. In this situation, consideration should be given to adding hepatitis A vaccine to the prevention plan for unvaccinated children and staff in the involved center(s).

Residents of institutions for developmentally disabled persons. Historically, hepatitis A virus infections were common among persons with developmental disabilities living in institutions. The occurrence of HAV infection has diminished, and routine vaccination against hepatitis A is no longer recommended for this population.

All susceptible persons traveling to or working in countries that have high or intermediate rates of hepatitis A should be vaccinated or receive immune globulin (IG) before traveling. Persons from developed countries who travel to developing countries are at high risk for hepatitis A. The risk for hepatitis A exists even for travelers to urban areas, those who stay in luxury hotels, and those who report that they have good hygiene and that they are careful about what they drink and eat. For more information on international travel and HAV, see CDC's travel page at http://wwwn.cdc.gov/travel/yellowBookCh4-HepA.aspx .

The first dose of hepatitis A vaccine should be administered as soon as travel is considered.

Previously, hepatitis A vaccination was recommended to be administered at least 2–4 weeks before departure to an area with intermediate or high rates of hepatitis A. Travelers who were departing in less than 2 weeks were recommended to receive IG for short-term protection.

However, on the basis of data indicating that immune globulin and vaccine have equivalent postexposure efficacy among healthy persons aged 1–40 years, the Advisory Committee on Immunization Practices (ACIP) has amended its guidelines for hepatitis A vaccination for travelers. ACIP now recommends that one dose of single-antigen hepatitis A vaccine administered at any time before departure may provide adequate protection for most healthy persons.

For optimal protection, older adults, immunocompromised persons, and persons with chronic liver disease or other chronic medical conditions who are planning to depart in <2 weeks should receive the initial dose of vaccine and also can simultaneously be administered IG (0.02 mL/kg) at a separate anatomic injection site.

Travelers who are allergic to a vaccine component or who elect not to receive vaccine should receive a single dose of immune globulin (0.02 mL/kg), which provides effective protection against hepatitis A virus infection for up to 3 months. Travelers whose travel period exceeds 2 months should be administered immune globulin at 0.06 mL/kg; administration must be repeated if the travel period exceeds 5 months.

Immune globulin is recommended because hepatitis A vaccine is currently not licensed for use in this age group.

Until recently, an injection of immune globulin (IG) was the only recommended way to protect people after they have been exposed to hepatitis A virus. In June 2007, U.S. guidelines were revised to allow for hepatitis A vaccine to be used after exposure to prevent infection in healthy persons aged 1–40 years.

• For healthy persons aged 12 months–40 years, single-antigen hepatitis A vaccine at the age-appropriate dose is preferred to IG because of vaccine’s advantages, including long-term protection and ease of administration, as well as the equivalent efficacy of vaccine to IG.
• For persons aged >40 years, IG is preferred because of the absence of information regarding vaccine performance in this age group and because of the more severe manifestations of hepatitis A in older adults. Vaccine can be used if IG cannot be obtained. The magnitude of the risk of HAV transmission from the exposure should be considered in decisions to use vaccine or IG in this age group.
• For children aged <12 months, immunocompromised persons, persons with chronic liver disease, and persons who are allergic to the vaccine or a vaccine component, IG should be used.

Close personal contacts. Close personal contacts of persons with serologically confirmed hepatitis A (i.e., through a blood test), including:

• Household and sex contacts
• Persons who have shared illicit drugs with someone with hepatitis A

Consideration should also be given to providing IG or hepatitis A vaccine to persons with other types of ongoing, close personal contact with a person with hepatitis A (e.g., a regular babysitter or caretaker).

Child-care center staff, attendees, and attendees' household members

• PEP should be administered to all previously unvaccinated staff and attendees of child care centers or homes if 1) one or more cases of hepatitis A are recognized in children or employees or 2) cases are recognized in two or more households of center attendees.
• In centers that provide care only to older children who no longer wear diapers, PEP need be administered only to classroom contacts of the index patient (i.e., not to children or staff in other classrooms).
• When an outbreak occurs (i.e., hepatitis A cases in three or more families), PEP should also be considered for members of households that have diaper-wearing children attending the center.

Persons exposed to a common source, such as an infected food handler. If a food handler receives a diagnosis of hepatitis A, PEP should be administered to other food handlers at the same establishment. Because transmission to patrons is unlikely, PEP administration to patrons typically is not indicated but may be considered if 1) during the time when the food handler was likely to be infectious, the food handler both directly handled uncooked foods or foods after cooking and had diarrhea or poor hygienic practices, and 2) patrons can be identified and treated within 2 weeks of exposure.

In settings in which repeated exposures to HAV might have occurred, such as institutional cafeterias, stronger consideration of PEP use might be warranted.

If a single case of hepatitis A is identified in a school (other than a child care setting in which children wear diapers), office, or other work setting, and if the source of infection is outside the school or work setting, PEP (i.e., injection of IG or hepatitis A vaccine) is not routinely recommended. Similarly, when a person who has hepatitis A is admitted to a hospital, staff should not routinely be administered PEP; instead, careful hygienic practices should be emphasized.

However, if it is determined that hepatitis A has been spread among students in a school or among patients and staff in a hospital, PEP should be administered to unvaccinated persons who have had close contact with an infected person.

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