Vaccines

Hepatitis A

Updated: February 10, 2006

Table of Contents

    Understanding the Disease

    Hepatitis A infection is caused by the hepatitis A virus (HAV).

    When infected by hepatitis A virus, adolescents and adults are more likely than young children to develop signs and symptoms of disease, including fever, weakness, nausea, abdominal pain, dark urine, and yellow eyes and skin, and are more likely to experience severe disease.

    Symptoms usually last less than two months, but 10% to 15% of those infected will have prolonged or relapsing disease lasting up to six months. Unlike hepatitis B and C, chronic hepatitis A disease does not occur. Unfortunately, each year in the U.S. 125,000 to 200,000 people become sick with hepatitis A. In the US, 70 to 100 people die― mostly those with underlying liver disease.

    Most hepatitis A disease occurs in community-wide outbreaks. This virus is most commonly spread in stool, although it can be spread through contact with infected blood. Infection is transmitted from person to person in households and extended family settings. Outbreaks sometimes occur when many people have eaten from the same hepatitis A-infected food source but almost half of people have no identified risk factor. Infected people are most likely to spread hepatitis A virus during the two-week period before they know they are infected. Since most infected pre-school children show no symptoms of hepatitis A infection, they often unknowingly spread the hepatitis A virus to others.

    Prior to the introduction of hepatitis A vaccine, about one-third of the hepatitis A cases in the U.S. occurred in children 5 to 14 years of age. The lowest rate of infection was in adults more than 40 years old. The rates of infection and disease were much greater in some areas of the country than others.

    Available Vaccines

    The hepatitis A vaccine is available as:

    • HAV (alone)
    • HAV in combination with hepatitis B (HBV) vaccine

    Product: Havrix® (HAV)
    Manufacturer: GlaxoSmithKline
    Year Licensed: 1995

    Product: Vaqta® (HAV)
    Manufacturer: Merck
    Year Licensed: 1996

    Product: Twinrix® (HAV and HBV combination vaccine)
    Manufacturer: GlaxoSmithKline
    Year Licensed: 2001

    For information on the thimerosal content in these vaccines, see:

    History of the Vaccine

    Hepatitis A vaccine was introduced incrementally first for children living in communities with the highest rates of disease (1996) and then for children living in States/communities with consistently elevated rates of infection (1999). The impact of immunization with hepatitis A vaccine has been a dramatic decline in the rates of disease and a sharp reduction in the groups with the highest risk of infection, native Americans and Alaskan natives. Rates of hepatitis A infection are now similar in most areas of the US. As a consequence, hepatitis A vaccine has now been recommended for all children in the US 12-23 months of age to eliminate hepatitis A transmission nationally.

    Who Should and Should Not Receive the Vaccine

    Who should receive the vaccine?

    • Children should receive hepatitis A vaccine at one year of age (i.e. 12-23 months). Vaccination should be completed according to the licensed schedules. Catch up programs for unvaccinated children 2-18 years of age should be considered.
    • Children who were not vaccinated by 2 years of age can be vaccinated at subsequent visits. · States, counties, and communities with existing hepatitis A vaccination programs for 2-18 year olds (i.e. those in the areas where vaccination was initially targeted because of high rates of disease) should continue to maintain these programs.
    • People traveling to or working in countries that have high or intermediate rates of infection, such as those located in Central or South America, the Caribbean, Mexico, Asia (except Japan, Australia and New Zealand), Africa, and eastern Europe. The vaccine series should be started at least one month before traveling.
    • Men who have sex with men
    • People who use illicit drugs
    • People who work with HAV-infected primates or HAV in a laboratory
    • People who receive clotting factor concentrates
    • People infected with other hepatitis viruses
    • People with chronic liver disease who are not already immune to HAV
    • People who have received, or are waiting to receive, a liver transplant
    • Food handlers should consider getting the HAV vaccine.
    • People aged 18 and older who are at risk for both HAV (based on the above risk factors) and HBV may receive the hepatitis A and B combination vaccine. Adults are at risk for hepatitis B virus infection if they have had more than one sex partner during a six month period; are health care workers, or are otherwise exposed to infected blood or body fluids; are men who have sex with other men; or use injection drugs.

    Who should not receive the vaccine?

    • Those who have had a serious adverse reaction to a previous dose of the vaccine or its ingredients should not receive another dose.
    • People who are moderately or severely ill should consult with their physician before receiving any vaccine.
    • The safety of hepatitis A vaccine for pregnant women is not yet known, but any risk to either the pregnant woman or the fetus is thought to be very low.

    This vaccine is recommended by:

    • Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention
    • American Academy of Pediatrics
    • American Academy of Family Physicians
    • American Thoracic Society

    The complete childhood immunization schedule can be found at:
    www.cdc.gov/nip/recs/child-schedule.pdf

    The summary of adolescent/adult immunization recommendations can be found at:
    www.cdc.gov/nip/recs/adult-schedule.pdf

    Dose Schedule

    Hepatitis A vaccines are given in two doses. Anyone two years of age or older may receive the first dose. The timing of the second dose depends upon which manufacturer’s vaccine is administered. Though preferable, it is not necessary to receive the same manufacturer’s hepatitis A vaccine for both doses. Both hepatitis A vaccines have pediatric and adult formulations.

    • Havrix®1 (GlaxoSmithKline): The second dose should be given 6 to 12 months after the first.
    • Vaqta® (Merck): For those aged 12 months to 18 years, the second dose should be given 6 to 18 months after the first. For people over 18 years, the second dose should be given 6 to 12 months after the first.
    • The hepatitis A and B combination vaccine (Twinrix®, GlaxoSmithKline) is approved for people 18 years and older and is given on a 0-, 1-, and 6-month schedule.
    • 1. NNii uses vaccine trade names only for clarity in our presentation of immunization recommendations. NNii does not recommend specific vaccine brands over others.

    Effectiveness of the Vaccine

    Between 97% and 99% of healthy people two years of age or older who receive two doses of the vaccine are protected from HAV infection. Immunity usually develops within four weeks after the initial dose. After two doses of the vaccine, it is estimated that immunity will last for at least 20 years.

    Researchers are working to determine how effective the Hepatitis A vaccine is at preventing the disease if it is administered after a person has already been exposed to the virus.

    Known Side Effects

    About half of those who receive the vaccine will have no side effects. Most others will have only a mild reaction, such as:

    • Soreness at the injection site (56% of those who get the vaccination)
    • Headache (14% of those who get the vaccination)
    • Temporary weakness (7% of those who get the vaccination)

    If these problems occur, they usually come 3-5 days after vaccination and last for 1 or 2 days.

    No serious adverse events have been attributed to the hepatitis A vaccine. In very rare cases a person may be allergic to some component of the vaccine (such as a preservative). Signs of allergic reaction can include difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness.

    Related Issues

    Hepatitis A may be widely spread through contaminated food. In 1983, for example, 203 people became ill in a county of 7,800 in Oklahoma. Ninety-two percent of those infected had eaten at the same drive-in restaurant between two and six weeks before onset of illness.

    Unlike hepatitis B, mothers infected with hepatitis A rarely transmit the disease to their newborns.

    The hepatitis A and B combination vaccine has been shown to be as safe and effective as HAV and HBV vaccines given separately.

    Key References and Sources of Additional Information

    CDC Information

    http://www.cdc.gov/nip/publications/VIS/vis-hep-a.pdf