Hepatitis, which translates to inflammation of the liver, is a widespread global infection. Fortunately, the two most common forms—Hepatitis A and Hepatitis B—are highly preventable through vaccination. The liver is a critical organ responsible for filtering blood, aiding digestion, and maintaining overall health, making its protection a top health priority.
Below, we explain how the Hepatitis A and B vaccines work, detail their impressive effectiveness, discuss how long immunity lasts, and provide clear recommendations on who should receive these vital immunizations.
Hepatitis A and B Vaccines: How They Work
The Hepatitis A and Hepatitis B vaccines are both inactivated vaccines. This means they utilize dead or inactivated strains of the respective hepatitis virus. These safe components teach your immune system how to recognize and mount a defense against a real infection should you ever be exposed. It is essential to remember that while you may experience mild side effects, you cannot contract Hepatitis from the vaccine itself.
Available Hepatitis Vaccines
Full protection requires multiple doses. The three available vaccines that offer protection against Hepatitis A and B are:
- Hepatitis B Vaccine: Administered to infants, children, and adults to protect against Hepatitis B only. This vaccine is given in two or three doses, depending on the brand used.
- Hepatitis A Vaccine: Administered to infants, children, and adults to protect against Hepatitis A only. This vaccine requires two doses, given several months apart.
- Hepatitis A and B Combination Vaccine: Given to adults to protect against both types. In the U.S., the approved combination vaccine (known by the brand name Twinrix) is typically administered in a series of three doses.
The Mechanism of Protection
Vaccines work by safely exposing the body to the virus's form, prompting the immune system to produce antibodies. These antibodies act as long-term memory cells. If you receive the full vaccine series and are later exposed to Hepatitis A or B, these antibodies will be present to quickly recognize and fight off the harmful virus, providing durable, long-term protection.
Effectiveness and Duration of Protection
The Hepatitis vaccines are considered highly successful public health tools, drastically reducing disease incidence globally.
Effectiveness Against Hepatitis B
Since the Hepatitis B vaccine was added to the routine childhood schedule, cases of the disease have declined significantly, virtually eliminating new infections in children and young adults under 19. Studies show that 90% to over 95% of infants, children, teenagers, and young adults develop protective antibody levels after completing the full series.
For those who delay or skip vaccination, exposure to Hepatitis B can lead to chronic, serious conditions, including lifelong infection, cirrhosis, liver cancer, and death. Vaccination offers 80–100% protection against these severe outcomes.
Effectiveness Against Hepatitis A
Since its introduction in 1996, the Hepatitis A vaccine has also dramatically reduced disease incidence. Even a single dose has been shown to provide immunity for several years for at least 94% of recipients, with the two-dose series offering robust, long-term protection.
Hepatitis A remains the most common vaccine-preventable illness contracted during international travel outside of the U.S., highlighting the need for vaccination before global trips.
How Long Does Immunity Last?
Research suggests that protection following the full Hepatitis B vaccine series lasts for at least 20–30 years, and potentially lifelong. Similarly, protection from the Hepatitis A vaccine is thought to last at least 25 years in adults and 14–20 years in children, with lifelong immunity considered probable for most people who complete the series.
Hepatitis Vaccine Schedule and Recommendations
Health organizations recommend that nearly everyone be vaccinated against Hepatitis A and B. However, you should consult your doctor for a schedule tailored to your health history.
General Vaccination Recommendations
Vaccination is generally recommended for:
- All infants.
- Children and adolescents under 19 years old who were not previously vaccinated.
- Adults aged 19 through 59 who have not been vaccinated or are unsure of their status.
- Adults aged 60 and older who wish to be protected, even without known risk factors for Hepatitis B.
Specific Risk Groups
One or both vaccines are highly recommended for the following groups due to increased exposure risk:
- International travelers.
- People with occupational risk of infection (e.g., healthcare workers).
- People who use illegal injectable or noninjectable drugs.
- Men who have sexual contact with other men.
- Sexually active individuals who are not in long-term, mutually monogamous relationships.
- People seeking treatment for a sexually transmitted infection (STI).
- People with chronic liver disease, chronic kidney disease (end stage), or Hepatitis C.
- People living with HIV or diabetes.
- Staff and residents of institutions or group homes.
- Household members and intimate partners of people with chronic Hepatitis B infection.
Child and Teen Vaccine Schedule
Following the recommended schedule is critical for ensuring full protection:
Hepatitis B Vaccine (3 Doses):
- First dose: Within 24 hours of birth.
- Second dose: At 1–2 months old.
- Third dose: At 6–18 months old.
Hepatitis A Vaccine (2 Doses):
- First dose: At 12–23 months old.
- Second dose: At least 6 months after the first dose.
Infants aged 6 to 11 months traveling internationally should receive a dose before travel. This dose does not count toward the long-term two-dose series, which should still be completed starting at 12 months.
Recommendations for Pregnant Women
The CDC recommends that pregnant women with risk factors for Hepatitis A and B who are unvaccinated should receive the vaccines during pregnancy. Both vaccines are safe for pregnant women, and since they are inactivated, the risk of complications for the baby is extremely low. The benefits of vaccination significantly outweigh the risks for those with exposure risk.
Possible Side Effects of Hepatitis Vaccines
Side effects from the Hepatitis A or B vaccines are rare and typically mild. They may include:
- Tenderness, swelling, warmth, redness, or a lump at the injection site.
- Headache or nausea.
- Low-grade fever (up to 100.4°F or 38°C).
- Loss of appetite.
In extremely rare instances, severe, life-threatening allergic reactions can occur. If you or your child experience symptoms such as difficulty breathing, swelling of the face or throat, dizziness, weakness, or a fast heartbeat after vaccination, call 911 or go to the nearest hospital immediately.
Frequently Asked Questions: Hepatitis Vaccines
A. Hepatitis A is generally spread through contact with contaminated food or water (fecal-oral route). Hepatitis B is spread through contact with infected blood or bodily fluids, primarily through sexual contact, sharing needles, or from mother to child at birth.
A. Yes. The first dose of the Hepatitis B vaccine is safely administered to newborns within 24 hours of birth. This initial dose is crucial for protecting the infant, especially if the mother’s Hepatitis B status is unknown or positive.
A. The combination vaccine (Twinrix) is only approved for adults and provides simultaneous protection against both viruses in a single series of injections, reducing the total number of shots required for full immunity.