Hepatitis A: The Disease & Vaccines

Hepatitis A: The Disease & Vaccines

The hepatitis A vaccine is recommended for all children between 12 months and 18 years of age living in the United States. It is also recommended for others who are considered to be at increased risk of infection, including:

  • Those traveling to countries with moderate or high rates of hepatitis A
  • Those in close contact with a child adopted from a country with moderate or high rates of hepatitis A
  • People experiencing homelessness
  • Men who have sex with men
  • People who use injection or non-injection drugs
  • People with chronic liver disease or HIV infection
  • People with increased risk of exposure because of their job
  • Pregnant women who might be at increased risk
  • Unvaccinated people 1 year of age and older who are at risk for hepatitis A during outbreaks
  • People who have been exposed to hepatitis A in the last two weeks (known as postexposure prophylaxis).  

The hepatitis A vaccine is typically given as a series of two shots — the second administered at least 6 months after the first. Children receiving the first shot should be at least 1 year old. Those up to 18 years old who have not been vaccinated against hepatitis A should get the vaccine.

Because hepatitis A outbreaks occur each year in the U.S., adults who wish to be protected against the disease can be vaccinated. (For more information about recent outbreaks, see "Why are recent hepatitis A outbreaks concerning to health officials?" in the "Other questions you might have" section lower on this page.)

If an unvaccinated person 1 year of age or older is exposed to hepatitis A, they should get one dose of hepatitis A vaccine within 2 weeks of exposure. This is called postexposure prophylaxis.  These individuals should get a second dose 6 months after the first dose for long-term protection.

The threat of hepatitis A virus

Although the threat of hepatitis A virus infection is high in developing countries, the United States is not, by any means, hepatitis A virus-free. Each year, about 1,000-17,500 people in the United States, many of whom are children, contract hepatitis A virus. And every year about 75 people die from hepatitis A virus infection. As a result, the Centers for Disease Control and Prevention (CDC) recommends that all children get the hepatitis A vaccine between 12 and 23 months of age. Those up to 18 years of age who have not previously received hepatitis A vaccine should also be vaccinated.

The disease

What is hepatitis A virus?

Hepatitis A is a virus that causes hepatitis (inflammation of the liver). Symptoms can include fever, jaundice (a yellowing of the skin or eyes, dark urine, clay-colored bowel movements), tiredness, nausea and vomiting. Young children are much less likely to develop symptoms when they are infected with hepatitis A virus than adults.

How do you catch hepatitis A virus?

People infected with hepatitis A virus excrete the virus in their stools. You can catch the virus in a number of ways:

  • Babies with hepatitis A virus will have diapers that are contaminated with the virus. Adults changing these diapers are likely to get infected if they don't carefully wash their hands with soap and water after handling the diaper.
  • Because hepatitis A virus is present in the stools of people who are infected, countries or cities with low standards for the handling and disposal of sewage have an enormous problem with hepatitis A virus infections. The problem is that the virus quickly enters the water supply and contaminates anything that comes in contact with the water, including food. It is probably not unrealistic to think about many developing countries as having a thin layer of hepatitis A virus that covers anything that you could put into your mouth.
  • People working in the food industry who are infected and do not exercise appropriate hand washing techniques between using the restroom and handling food have also been known to spread the infection.

Unfortunately, people infected with hepatitis A can transmit the virus to others up to two weeks before they have symptoms, so they may be infecting others without even knowing they have hepatitis A themselves.

How can you avoid catching hepatitis A virus when traveling?

Anyone traveling to countries where hepatitis A virus infections are common should avoid the following:

  • Ice and unbottled water
  • Uncooked shellfish
  • Uncooked or unpeeled vegetables and fruit
  • Food from street vendors
  • Salads

Vaccination at least 2 weeks before travel is generally also recommended. Additional travel information is available in the CDC travel publication, Yellow Book.

Salad bowl

Hepatitis A Q&A

The vaccine

How is the hepatitis A vaccine made?

The hepatitis A vaccine is made by taking whole hepatitis A virus and killing it with the chemical formaldehyde. Because the virus is inactivated, it cannot possibly cause hepatitis (see How Are Vaccines Made?).

Does the hepatitis A vaccine have side effects?

The hepatitis A vaccine can cause pain, redness and tenderness where the shot was given. The vaccine can also cause headache in about 5 of every 100 recipients. The hepatitis A vaccine has been given to millions of people without serious side effects.

Who should get the hepatitis A vaccine?

The hepatitis A vaccine should be given to the following groups of people:

  • Children 1 year of age and older
  • Those traveling to countries with moderate or high rates of hepatitis A
  • Those in close contact with a child adopted from a country with moderate or high rates of hepatitis A
  • People experiencing homelessness
  • Men who have sex with men
  • People who use injection or non-injection drugs
  • People with chronic liver disease or HIV infection
  • People with increased risk of exposure because of their job
  • Pregnant women who might be at increased risk
  • Those who want to be protected against hepatitis A
  • Unvaccinated people 1 year of age and older who are at risk for hepatitis A during outbreaks
  • Unvaccinated people exposed to hepatitis A in the last two weeks (known as postexposure prophylaxis).

Other questions you might have

Why are recent hepatitis A outbreaks concerning to health officials?

On April 7, 2023, the CDC reported a hepatitis A outbreak in the Morbidity and Mortality Weekly Report (MMWR). The reported outbreak occurred in Virginia between September 2021 and September 2022. While much of the report shares details that we are all familiar with when it comes to hepatitis A, several aspects of this outbreak should raise concern among healthcare providers across the country:

  1. The first case was in an infected restaurant worker who worked at three locations while infectious, and while this resulted in 51 cases, more concerning was evidence of sustained community transmission in the months that followed. This community spread led to an additional 98 cases of hepatitis A.
  2. Due to lack of contact information and one refusal to share information, public health officials were unable to get information from more than half of the individuals with community-acquired infections.
  3. While we know the risk factors most commonly associated with hepatitis A (homelessness, drug use, male-to-male sexual contact, and incarceration), few of the individuals exposed by the infected restaurant worker had risk factors. Yet, more than 60% were hospitalized, three died, and one required a liver transplant.
  4. A 2013 Substance Abuse and Mental Services Administration survey found that the restaurant industry had the highest rates of employees who reported using drugs in the month before the survey. While these data are not recent, they indicated that 1 in 5 respondents working in the food industry were affected, putting them at greater risk of hepatitis A infections.
  5. Despite public health efforts to vaccinate employees of the affected restaurants, including on-site vaccination clinics, fewer than 20% of the eligible employees were vaccinated.

Given the number of people who dine out and the potential for unvaccinated, increased-risk food workers, a hepatitis A infection could easily affect any individual, family or community. While most people recover, not all do, and some recover only after significant healthcare interventions. The Virginia outbreak and ongoing transmission cost more than $3 million.

The hepatitis A vaccine can be used for any individual who wants protection against this infection. We should ensure that all patients and families are aware of this opportunity for protection.

Read the MMWR report.

What is hepatitis?

Hepatitis is a medical term used to describe inflammation of the liver. However, because some viruses include the word “hepatitis” in their name, it is easy to be confused. Typically, an inflamed liver is not functioning properly, leading to symptoms like nausea or vomiting, pain, dark urine, light-colored bowel movements or diarrhea, joint pain, or yellowing of the skin or the whites of the eyes (called jaundice). However, not everyone with hepatitis experiences symptoms, making it difficult in some cases to know that a person’s liver is under stress.

Hepatitis can be caused by several viruses. Hepatitis A, hepatitis B, and hepatitis C may come to mind when one thinks about liver infections (perhaps even the less commonly known, hepatitis D and hepatitis E), but hepatitis can result from a variety of causes, including:

  • Other viruses, such as adenovirus, cytomegalovirus, Epstein-Barr virus, herpes simplex virus, Yellow fever virus and Dengue virus
  • Bacterial infections, particularly if they are severe enough to infect the bloodstream (called sepsis)
  • Repeated consumption of large amounts of alcohol over time
  • Chemicals, including poisons or medications
  • Autoimmune disorders
  • Genetic disorders, such as Wilson disease
  • Dietary supplements

The condition can be short-lived or chronic, meaning it does not resolve and eventually can lead to liver disease or liver cancer, such as can occur with hepatitis B infections.

Are infections caused by hepatitis A virus similar to those caused by hepatitis B virus?

Although hepatitis A virus sounds like it would be similar to hepatitis B virus, the viral infections are really quite different. Hepatitis B virus can cause long-term problems, such as cirrhosis (chronic liver damage) and liver cancer. On the other hand, hepatitis A virus doesn't cause long-term problems. Also, hepatitis B virus kills about 750 people every year, whereas hepatitis A virus kills about 75 people every year. Finally, hepatitis B virus is transmitted by coming in contact with someone who is infected, but hepatitis A virus is typically transmitted in contaminated food or water.

How long should I wait after getting the hepatitis A vaccine before I travel?

The hepatitis A vaccine is most effective if given at least four weeks before traveling, but the vaccine is still somewhat effective if given at least two weeks before traveling.

If you are 40 years of age and older, are immunocompromised, or have chronic liver disease and are going to travel within two weeks of receiving the vaccine, you may also be recommended to get a dose of  "immunoglobulin." Immunoglobulin contains antibodies directed against hepatitis A virus. You don't develop long-lived protection by receiving immunoglobulin, but  the antibodies will help protect you during the trip. Protection afforded by immunoglobulin lasts several months. The second dose of hepatitis A vaccine should be received 6 months after the first dose for long term protection.

Why was the hepatitis A vaccine recommended for all children 2 to 18 years old after it was given to only certain groups at first?

When the hepatitis A vaccine first became available in the United States, it was only recommended for specific people who were at increased risk of getting hepatitis A. However, in 2006 the recommendation was extended to include all infants between 12 months and 23 months of age. The recommendation was updated again in 2020 to include vaccination of all children between 2 and 18 years of age who were not previously vaccinated against hepatitis A.

  • Originally, the vaccine could only be given to children 2 years of age or older. In 2006, following additional studies, use of the vaccine was expanded to include infants between 12 months and 23 months of age.
  • Disease rates had been controlled in parts of the country where the vaccine was recommended, yet cases of hepatitis A were still occurring, particularly in regions where children were not regularly getting the vaccine. So, the recommendation was expanded to protect children in all parts of the country.

Relative risks and benefits

Do the benefits of the hepatitis A vaccine outweigh the risks?

Hepatitis A virus infections are quite common throughout the world. So common, in fact, that it is really easier to list the countries where you are unlikely to catch the infection than countries where you are likely to catch it. Also, the United States still has 1,000-17,500 cases of hepatitis A virus every year. Although hepatitis A virus infections do not cause long-term liver damage, about 75 people die every year from severe, overwhelming infections caused by the hepatitis A virus. Because the vaccine does not have serious side effects, the benefits of the hepatitis A vaccine clearly outweigh its risks.

Disease risks

  • Inflammation of the liver
  • Fever
  • Vomiting
  • Jaundice
  • Nausea

Vaccine risks

  • Pain, redness, and tenderness at the injection site
  • Headache (5 of 100)

References

Walsh NM, Soeters HM, Nelson NP, Khudyakov Y, and Weng MK. "Hepatitis A Vaccines" in Orenstein WA, Offit PA, Edwards KM, and Plotkin SA, Eds. Plotkin’s Vaccines, 8th Edition, 2024, Elsevier.

Centers for Disease Control and Prevention. 2020 Viral Hepatitis Surveillance Report. Published September 2022.

Reviewed by Paul A. Offit, MD, on May 23, 2023