Vaccine
Talk

What is hepatitis A?

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.

What are the signs and symptoms of hepatitis A?

Illness 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.

How is hepatitis A virus (HAV) transmitted?

Person-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.

What is the incubation period for hepatitis A?

HAV can produce either asymptomatic or symptomatic infection in humans after an average incubation period of 28 days (range: 15–50 days).

Are people with chronic liver disease at higher risk of acquiring HAV infection?

No. 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.

Can hepatitis A virus (HAV) be transmitted by blood?

Yes. 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.

Is HAV transmitted by saliva?

In experimentally infected nonhuman primates, HAV has been detected in saliva during the incubation period; however, transmission by human saliva has not been reported.

How stable is HAV in the environment?

Depending on conditions, HAV can be stable in the environment for months; freezing does not inactivate 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 (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.

Do people with hepatitis A develop chronic disease or can they get repeated infections?

No, 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.

For hepatitis A vaccination, is the minimum interval the same as 24 weeks?

No. The minimum interval between dose #1 and #2 of HepA vaccine is 6 calendar months, not 24 weeks.

A child received dose 2 four months after dose 1. Repeat?

Yes. 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 the 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.

What are the recommendations for postexposure prophylaxis (PEP)?

In 2020, CDC published revised recommendations for hepatitis A postexposure prophylaxis (PEP). See the complete recommendations at this CDC document, especially Table 4 (page 19) and Appendix B (page 36). Healthy people who have completed the HepA vaccination series at any time do not need additional PEP if exposed. People age 12 months and older exposed 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.

Can hepatitis A vaccine be administered during pregnancy?

Yes. ACIP recommends that pregnant people at risk for HAV infection during pregnancy or at risk for a severe outcome from HAV infection should be vaccinated during pregnancy if not previously vaccinated. Pregnant people should be vaccinated for the same indications as non‑pregnant people.

Can lactating women receive HepA vaccine? Can it be coadministered?

Yes. HepA vaccine is an inactivated vaccine and poses no harm to the nursing infant. Other inactivated and/or live virus vaccines can be administered at the same time as HepA vaccine, preferably at a different anatomical site; if in the same muscle, separate injections by at least 1 inch.

What if dose #2 is delayed?

You do not need to restart the series. One dose provides 94%–100% immunogenicity with documented protection lasting more than 10 years. Administer the second dose to ensure optimal long‑term protection.

Pediatric dose given to an adult by mistake—what to do?

If discovered the same clinic day, administer the additional half dose that day. If discovered later, do not count the pediatric dose; recall the person and give a full age‑appropriate repeat dose. If an adult dose is given to a child, count it as valid but notify the parent; the child should still receive the second dose on schedule.

If a person previously had HAV infection, should they still receive vaccine for travel?

No—provided there is documentation of prior infection (positive total anti‑HAV). If uncertain, administer HepA vaccine and/or immune globulin (IG). Vaccinating someone who is already immune will not cause harm.

Can HepA vaccine be given to immunocompromised people?

Yes. All people age 1 year or older living with HIV infection should be vaccinated against hepatitis A if not already vaccinated, regardless of CD4+ count. Any immunocompromised person with risk factors (for example, international travel or drug use) should receive HepA vaccine.

Is it okay to vaccinate a patient on interferon for hepatitis C?

Yes. HepA vaccine should be given to all susceptible patients with chronic liver disease. HepA vaccine is highly immunogenic.