Hepatitis A is a liver disease common in many parts of the world and caused by hepatitis A virus (HAV), a picornavirus that causes acute inflammation of the liver. It is not related to the common viruses that cause hepatitis B or C.
Last reviewed: June 25, 2023Illness caused by HAV infection cannot be distinguished from other types of acute viral hepatitis, but it typically has an abrupt onset that can include fever, malaise, anorexia, nausea, abdominal discomfort, dark urine, and jaundice. The likelihood of having symptoms with HAV infection is related to age. In children younger than age 6 years, 70% of infections are asymptomatic. When illness does occur in young children, it is typically not accompanied by jaundice. In older children and adults, infection typically is symptomatic, with jaundice occurring in more than 70% of patients.
Hepatitis A signs and symptoms usually resolve in 2-3 months, although 10% to 15% of symptomatic people have prolonged illness (usually referred to as relapsing hepatitis A) lasting up to 6 months and should be considered infectious during that time.
Last reviewed: June 25, 2023Person-to-person spread through the fecal-oral route is the primary means of HAV transmission. Peak infectivity in infected people occurs during the two-week period before the onset of jaundice when the concentration of virus in the stool is highest and most people are no longer infectious one week after jaundice onset. Before routine vaccination of children was recommended, children were a key source of infection because most infected children had no symptoms and could shed virus in stool for weeks or months. Transmission currently occurs primarily among susceptible adults.
Common-source outbreaks and sporadic cases 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. Transmission of the virus from infected food handlers to food service establishment patrons is rare, accounting for 0.2% of the nearly 23,000 outbreak-associated cases of hepatitis A investigated by state health departments during 2016-2019. In 2020, there were 9,952 cases reported to public health, although CDC estimates that the actual number of cases was closer to 19,900. This represents a 47% decrease from 2019.
Until 2017, US incidence rates of hepatitis A were driven by occasional outbreaks, often linked to viral contamination of imported food. Since 2017, communitywide outbreaks have occurred more frequently, predominantly among people who are connected by specific risk factors, such as drug use or homelessness, and their close contacts.
Last reviewed: June 25, 2023HAV can produce either asymptomatic or symptomatic infection in humans after an average incubation period of 28 days (range: 15–50 days).
Last reviewed: June 25, 2023In infected people, HAV replicates in the liver, is excreted in bile, and is shed in stool. Peak infectivity occurs during the 2-week period before onset of jaundice or elevation of liver enzymes, when concentration of virus in stool is highest. Concentration of virus in stool declines after jaundice appears, with most people no longer infectious about a week after jaundice appears. Children can shed HAV for longer periods than adults, up to 10 weeks or longer after onset of clinical illness.
Last reviewed: June 25, 2023The incidence of hepatitis A in the US increased more than 10-fold from 2015 to 2019, with over 18,800 cases reported to CDC in 2019. The number of reported cases declined by 47% to 9,952 in 2020. This number is an underestimate of the actual number of infections: CDC estimates that about 19,900 cases actually occurred in 2020.
Between 2012 and 2015 the number of reported hepatitis A infections ranged from approximately 1200 to 1800 cases every year. Beginning in 2016, large foodborne outbreaks led to an increase in the number of cases and sustained, large person-to-person outbreaks began, primarily driven by infections among unvaccinated people who use drugs and people experiencing homelessness and their contacts. Since then, persistent person-to-person outbreaks have led to substantial increases in hepatitis A infection, with 37 states reporting almost 45,000 cases over the 7 years between the beginning of the outbreaks in 2016 and June 2023. The rate of new cases has declined substantially since the peak in 2019. More information regarding ongoing multistate outbreaks can be found here: www.cdc.gov/hepatitis/outbreaks/ongoing-hepatitis-a.
Last reviewed: June 25, 2023Yes. Death as a result of fulminant hepatic failure is rare, however, older age (over 40 years) and preexisting chronic liver disease increases the risk of severe disease and death from hepatitis A. The person-to-person U.S. multistate outbreaks that began in 2016 have disproportionately affected adults with chronic liver disease and other health problems related to drug use and unstable housing. From 2016 through June 2023, CDC received reports of nearly 45,000 cases of acute HAV infection. Of these, approximately 61% have been hospitalized and nearly 1% (more than 420 people) have died.
Last reviewed: June 25, 2023People who are at increased risk for acquiring HAV infection include the following:
Historically, HAV infection was highly endemic in institutions for people with developmental disabilities as a result of poor hand hygiene, close living conditions and diaper use. As fewer children have been institutionalized and as conditions in institutions have improved, the incidence and prevalence of HAV infection have decreased, although outbreaks can occur in these settings. All children with developmental disabilities should receive HepA vaccine according to U.S. routine vaccine recommendations, including catch up vaccination of all children through age 18 years.
As a strategy to further reduce the risk of hepatitis A outbreaks and reach adults in settings with a high proportion of people with risk factors for HAV infection, the current ACIP recommendations suggest considering HepA vaccination of residents and staff in facilities where hygiene is difficult to maintain, such as group homes for people with developmental disabilities and homeless shelters.
Last reviewed: June 25, 2023No. People with chronic liver disease are not at increased risk for acquiring HAV infection. However, they are at an increased risk for life-threatening, fulminant (severe and sudden) hepatitis if they become infected with hepatitis A. People considered to have chronic liver disease include those with hepatitis B or C infection, cirrhosis, fatty liver disease, alcoholic liver disease, and autoimmune hepatitis.
Last reviewed: June 25, 2023Hepatitis A cannot be differentiated from other types of viral hepatitis on the basis of clinical or epidemiological features alone. Appropriate blood tests must be used.
Total anti-HAV, which appears early in the course of infection, remains detectable for the person’s lifetime and indicates lifelong protection against the infection/disease. To confirm a diagnosis of acute HAV infection, serologic testing for IgM anti-HAV is required. In the majority of persons, serum IgM anti-HAV becomes detectable 5 to 10 days before onset of symptoms and lasts about 6 months. However, there have been reports of persons who test positive for IgM anti-HAV for up to a year or more following infection. An educational program on the interpretation of hepatitis A serology is available on the CDC website at www.cdc.gov/hepatitis/hcp/training/.
Last reviewed: June 25, 2023Yes. On rare occasions, HAV infection has been transmitted by transfusion of blood or blood products collected from donors during the viremic phase of their infection (i.e., when HAV is in the donor’s blood). Since 2002, tests to detect the presence of hepatitis A virus RNA in donated plasma have drastically reduced the risk of hepatitis A transmission from products derived from blood plasma.
Last reviewed: June 25, 2023In experimentally infected nonhuman primates, HAV has been detected in saliva during the incubation period; however, transmission by human saliva has not been reported.
Last reviewed: June 25, 2023Hospital-acquired HAV infection is rare. In the past, outbreaks were observed in neonatal intensive care units when infants acquired infection from HAV-infected transfused blood and subsequently transmitted HAV to other infants and staff. Outbreaks of hepatitis A caused by transmission from adult patients to healthcare personnel (HCP) are typically associated with fecal incontinence and inadequate hand hygiene, although the majority of hospitalized patients who have hepatitis A are admitted after onset of jaundice, when they are beyond the point of peak infectivity. Transmission in healthcare settings also has resulted from breakdowns in standard infection control practices and transmission from one healthcare provider to another.
Last reviewed: June 25, 2023Depending on conditions, HAV can be stable in the environment for months; freezing does not inactivate (i.e., render non-infectious) HAV. HAV is inactivated by heating foods to temperatures greater than 185°F (85°C) for 1 minute. In addition, HAV on surfaces is inactivated by disinfecting surfaces with a 1:100 dilution of sodium hypochlorite (i.e., household bleach) in tap water.
Adequately chlorinating water through water treatment processes and dilution in public water systems kills HAV. Spas and swimming pools that are adequately treated are not likely to pose a risk for HAV outbreaks.
Last reviewed: June 25, 2023No, there is no chronic (long-term) infection. Even the small proportion of people who develop relapsing HAV recover after about 6 months. Once you have had HAV infection and recovered, you cannot get it again.
Last reviewed: June 25, 2023Vaccination with the full series of hepatitis A vaccine (HepA) is the best way to prevent HAV infection. Immune globulin (IG) also can be used for short-term protection in certain situations.
Last reviewed: June 25, 2023| Recommended dosages and schedules of hepatitis A vaccines | |||||
| Vaccine | Age group | Dose | Volume | # Doses | Schedule |
| Havrix (GSK) | 1–18 years | 720 El.U.* | 0.5 ml | 2 | 0, 6–12 mos. |
| 19 years and older | 1440 El.U.* | 1.0 ml | 2 | 0, 6–12 mos. | |
| Vaqta (Merck & Co.) | 1–18 years | 25 U** | 0.5 ml | 2 | 0, 6–18 mos. |
| 19 years and older | 50 U** | 1.0 ml | 2 | 0, 6–18 mos. | |
*El.U. = Elisa Units **U = Units
| Combination vaccine using hepatitis A and hepatitis B vaccines | |||||
| Vaccine | Age group | Antigens used | Volume | # Doses | Schedule |
| Twinrix (GSK) | 18 years and older | Havrix (720 El.U.) combined with Engerix-B (20 mcg) | 1.0 ml | 3 | 0, 1, 6 mos. |
| 4 | 0, 7, 21-30 days, 12 months** | ||||
** Accelerated schedule may be used for rapid protection prior to travel or for rapid protection of an unexposed but at-risk person who also would benefit from hepatitis B protection. Twinrix is not recommended for use as post-exposure prophylaxis.
Last reviewed: June 25, 2023Yes, a number of studies indicate that the two brands of HepA, Havrix (GSK) and Vaqta (Merck), are interchangeable.
Last reviewed: June 25, 2023For detailed information about any vaccine shortage, go to CDC’s website at www.cdc.gov/vaccines/hcp/vaccines-us/shortages-delays.html.
Last reviewed: June 25, 2023The Advisory Committee on Immunization Practices (ACIP) recommends routine HepA vaccination for the following groups:
HepA vaccination is not routinely recommended for healthcare personnel, food handlers, sewage workers, or day care providers because there is no evidence that their occupational risks of HAV exposure are significantly higher than the general population. However, any person who desires protection from HAV infection may be vaccinated.
For details about CDC recommendations for the prevention of hepatitis A, see the 2020 recommendations of the Advisory Committee on Immunization Practices (ACIP): www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf.
Last reviewed: June 25, 2023Yes, unless the person is allergic to any of the vaccine components. HepA vaccination is safe and effective and is recommended for any person who wishes to obtain immunity.
Last reviewed: June 25, 2023All children should receive 2 doses of HepA vaccine beginning at age 1 year (i.e., 12–23 months). The 2 doses in the series should be administered at least 6 months apart. Any child age 2 through 18 years not previously vaccinated should be vaccinated. For a copy of the ACIP recommendations on hepatitis A, go to www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf.
Last reviewed: June 25, 2023No. The minimum interval between dose #1 and #2 of HepA vaccine is 6 calendar months, not 24 weeks.
Last reviewed: June 25, 2023Yes. The second dose was given more than 4 days before the minimum interval of 6 calendar months, so it is considered invalid and should be repeated. The repeat dose should be administered the proper minimum interval (6 months) after the invalid dose. If this repeat dose is inadvertently given less than 6 months after the invalid dose, it does not need to be repeated again as long as the interval between the initial HepA vaccine and the most recent dose is at least 6 calendar months.
Last reviewed: June 25, 2023In 2020, CDC published revised recommendations for hepatitis A postexposure prophylaxis (PEP). Please see the complete PEP recommendations at www.cdc.gov/mmwr/volumes/69/rr/pdfs/rr6905a1-H.pdf, with special attention to Table 4 on page 19 and Appendix B: Provider Guidance on Risk Assessment for Hepatitis A Postexposure Prophylaxis, beginning on page 36.
Healthy people who have completed the HepA vaccination series at any time do not need additional PEP if they are exposed to HAV. People who have recently been exposed to HAV and who have not received HepA vaccine previously should receive PEP as soon as possible, within 2 weeks of exposure.
People age 12 months and older exposed to HAV within the past 14 days and who have not previously completed the HepA vaccine series should receive a single dose of HepA vaccine as soon as possible. In addition to vaccine, immune globulin (IG; 0.1 mL/kg) may be administered to people older than age 40 years depending on the providers’ risk assessment. For long-term immunity, the HepA vaccine series should be completed with a second dose at least 6 months after the first dose. However, the second dose is not necessary for PEP. A second dose should not be administered sooner than 6 calendar months after the first dose, regardless of HAV exposure risk.
People age 12 months or older who are immunocompromised or have chronic liver disease, and who have been exposed to HAV within the past 14 days and have not previously completed the HepA vaccination series, should receive both IG (0.1 mL/kg) and HepA vaccine at the same visit in a different anatomic site (for example, separate limbs) as soon as possible after exposure. For long-term immunity, the HepA vaccination series should be completed with a second dose at least 6 months after the first dose. However, the second dose is not necessary for PEP. A second dose should not be administered sooner than 6 calendar months after the first dose, regardless of HAV exposure risk.
People with HIV infection develop protective levels of antibody more slowly and are less likely to develop protective antibody levels after vaccination with HepA, especially if their CD4+ count is low at the time of vaccination. Protection following vaccination of a person with HIV may wane over time. Vaccine should be administered if the exposed individual is not fully vaccinated; however, CDC also advises clinicians to consider administering IG PEP to an individual with HIV after a high-risk exposure (such as a household or sexual contact) even if the individual has been fully vaccinated.
Twinrix contains half the amount of hepatitis A antigen as a standard single-dose adult HepA vaccine. Twinrix should not be used for PEP but may be used to confer protection to at-risk but not yet exposed persons during an outbreak.
Infants younger than age 12 months and persons for whom vaccine is contraindicated should receive IG (0.1 mL/kg) instead of HepA vaccine as soon as possible and within 2 weeks of exposure. MMR and varicella vaccines should not be administered sooner than 6 months after IG administration in order to avoid possible IG interference with the effectiveness of MMR and varicella vaccines.
Last reviewed: June 25, 2023Prevaccination serologic testing for HAV (measuring either total anti-HAV or IgG anti-HAV) is not indicated for children because of the low prevalence of infection in children. It also is not routinely recommended for adults but may be considered in some settings to reduce costs associated with vaccinating people who are already immune. Prevaccination testing should not be used if it poses a barrier to vaccinating susceptible people, especially people who are difficult to access.
Prevaccination testing is most likely to be cost-effective for adults who were either born in or lived for long periods of time in areas of the world with high or intermediate hepatitis A endemicity. When evaluating people from populations with high rates of previous HAV infection, vaccination history also should be obtained, if feasible. If testing or vaccination history is not available, do not postpone vaccinating. There is no harm in vaccinating a person who has had natural infection or previous doses of vaccine.
Last reviewed: June 25, 2023Serologic testing for immunity to hepatitis A virus (HAV) is not necessary after routine HepA vaccination of infants, children or adults. Testing for the presence of anti-HAV antibody one month or more after completing the HepA vaccination series is recommended only for people whose future clinical management depends on knowing their immune status and for whom revaccination might be indicated, such as people living with HIV and other immunocompromised persons (such as transplant recipients and people vaccinated while receiving chemotherapy). In such individuals, if the results of postvaccination testing do not show an adequate immune response (10 mIU/mL or higher), revaccination with a complete series is recommended, followed by a second postvaccination serologic test. If that second test remains negative, no additional vaccination is recommended; however, the patient should be counseled on strategies to avoid exposure to HAV and the need for IG if an exposure occurs. If vaccination results in seroconversion, insufficient data are available to make recommendations concerning repeat testing, booster doses or revaccination.
Last reviewed: June 25, 2023ACIP recommends vaccination against hepatitis A virus (HAV) infection for all previously unvaccinated people who anticipate having close personal contact with an international adoptee from a country of high or intermediate endemicity during the first 60 days following the adoptee’s arrival in the U.S. In addition to the adoptee’s new parents and siblings, this group might include grandparents, other household members, regular babysitters and other caregivers. The first dose of HepA should be given to close contacts as soon as adoption is planned, ideally at least 2 weeks before the arrival of the adoptee. A second dose should be given no sooner than 6 months after the first dose.
Last reviewed: June 25, 2023The 2020 ACIP recommendations for the prevention of hepatitis A define a person experiencing homelessness as 1) a person who lacks housing (regardless of whether the person is a member of a family), including a person whose primary residence during the night is a supervised public or private facility (e.g., shelter) that provides temporary living accommodations and a person who is a resident in transitional housing, 2) a person without permanent housing who might: live on the streets, stay in a shelter, mission, single-room occupancy facility, abandoned building, vehicle, or any other unstable or nonpermanent situation, or 3) who is “doubled up”, a term that refers to a situation where persons are unable to maintain their housing situation and are forced to stay with a series of friends or extended family members. In addition, previously homeless persons who are to be released from a prison or a hospital might be considered homeless if they do not have a stable housing situation to which they can return. The instability of a person’s living arrangements is critical to the definition of homelessness.
Last reviewed: June 25, 2023While a complete series of HepA is recommended for long-term protection, even a single dose of HepA vaccine has been demonstrated to provide protection against hepatitis A for more than 10 years and can prevent or control outbreaks of hepatitis A. People who are experiencing homelessness may have difficulty protecting themselves from exposure to HAV in other ways because of their living conditions. They should be vaccinated when possible and provided a record of immunization. Reporting the HepA vaccination to a state immunization information system also can facilitate immunization assessment at future healthcare encounters.
Last reviewed: June 25, 2023No. A number of studies have shown that HCP are not at significantly increased risk of HAV infection because of their occupation. However, if HCPs are going to work (or vacation) in a country with a high or intermediate endemic rate of HAV infection, they are at risk of HAV infection and should be vaccinated. The only occupational indications for routine HepA vaccination are work with non-human primates or live HAV in a laboratory setting.
Last reviewed: June 25, 2023No. In the past, outbreaks of hepatitis A occurred among children in child care centers, infecting employees of those centers, especially those caring for infants and toddlers. Following widespread adoption of early childhood vaccination against hepatitis A, outbreaks in child care centers are now rare.
Last reviewed: June 25, 2023Although not at increased risk for hepatitis A virus (HAV) infection, people with chronic liver disease are at increased risk for fulminant hepatitis A, hospitalization, and death if they become infected with HAV. For this reason, HepA vaccination is recommended for them.
Last reviewed: June 25, 2023Twinrix is licensed as a 3-dose series for people age 18 years and older (minimum interval between dose 1 and dose 2 is 4 weeks; minimum interval between dose 2 and dose 3 is 5 months). It is also approved for use in an accelerated 4-dose schedule in adults, with doses given at 0, 7, and 21-30 days, followed by a booster dose at 12 months. There is no accelerated schedule for single antigen HepA or HepB vaccines, so the recommendations below presume the use of the Twinrix 3-dose routine schedule, with a minimum interval between dose 1 and dose 2 of 4 weeks.
If Twinrix is not available or if you choose not to use Twinrix to complete the hepatitis A (HepA) and hepatitis B (HepB) series, you should do the following:
Another way to consider this is as follows:
In published reports of three serologic surveys conducted among United States wastewater workers and appropriate comparison populations, no substantial or consistent increase in the prevalence of anti-HAV was identified among wastewater workers. No work-related instances of hepatitis A transmission have been reported among wastewater workers in the United States. In addition, in the United States, outbreaks of hepatitis A caused by flooding, which can carry raw sewage, have not been reported.
Last reviewed: June 25, 2023People with clotting factor disorders were originally recommended to receive hepatitis A vaccine (HepA) in 1996. At that time, the process used to make clotting factor supplements did not reliably inactivate hepatitis A viruses and recipients of these products had an increased risk of hepatitis A virus (HAV) infection. Modern blood donor screening and virus reduction steps have drastically reduced that risk. In addition, more than 80% of people with clotting factor disorders now receive recombinant clotting factor concentrates that are sterilized and have no risk of HAV transmission. As a result of these factors, people with clotting factor disorders now have no greater risk of hepatitis A than the general population and are no longer recommended to receive HepA vaccine unless it is otherwise indicated.
Last reviewed: June 25, 2023Because of measles. Measles is highly communicable and poses a serious threat to the health of unvaccinated infants. For this reason, all infants age 6 through 11 months who travel internationally are recommended to receive a dose of measles, mumps, and rubella vaccine (MMR) to reduce the risk of measles infection during travel.
The antibodies in immune globulin (IG) typically used to prevent HAV infection in infants before the first birthday can interfere with the effectiveness of MMR vaccine. An infant who is given IG should not be vaccinated with MMR or varicella vaccines for at least 6 months after IG administration. If an infant age 6 through 11 months is traveling to a destination where protection from infection with HAV is desired, ACIP recommends off-label use of HepA vaccine (not IG) in addition to MMR. The HepA and MMR doses administered before the first birthday do not count toward the routine vaccination series of either vaccine: these infant travelers will still need two doses of HepA and two doses of MMR when age appropriate.
Last reviewed: June 25, 2023