The hepatitis A vaccine is one of the most effective ways to prevent an acute hepatitis A infection. It is suitable for adults and children. However, in rare cases, vaccine ingredients may cause allergic reactions.

The hepatitis A virus is one of the primary causes of acute hepatitis infection worldwide.

Experts have linked the emergence of the hepatitis A vaccine to a significant decline in hepatitis A infections.

This article discusses how the hepatitis A vaccine works, the indications for vaccination, and possible side effects.

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The Centers for Disease Control and Prevention (CDC) recommends the following people get vaccinated against hepatitis A:

  • international travelers
  • males who have sexual contact with males
  • people who use injection or non-injection drugs
  • people who are at higher risk of infection with hepatitis A, such as medical professionals
  • people experiencing homelessness
  • people with HIV
  • people with chronic liver disease
  • people who are in direct contact with someone with hepatitis A
  • children over the age of 2 and adults who have not previously received the vaccine
  • children between 12 and 23 months old for a first dose, and a second dose 6 months later

People who have not been vaccinated and had direct contact with someone with hepatitis A should receive a hepatitis A vaccine either immediately or within 2 weeks after exposure.

Some common brand names for the hepatitis A vaccine include:

Other forms of the hepatitis A vaccine include:

  • Avaxim
  • Havrix
  • Healive
  • Havac

The hepatitis A vaccine works by stimulating an immune response, which triggers the production of antibodies against the inactive hepatitis A virus.

The vaccine contains an inactivated form of hepatitis A virus, also known as the vaccine antigen. When the immune system detects the antigen in the blood, it triggers the production of specific white blood cells called B and T-lymphocytes.

These lymphocytes develop specific antibodies and white cells that attack the vaccine antigen. This process also produces memory cells that help the immune system quickly identify and destroy the hepatitis A virus when a person is exposed.

Most vaccines also contain additional supporting ingredients known as adjuvants. These help strengthen the immune system’s response to a vaccine.

The adjuvant for the hepatitis A vaccine is aluminum, which helps:

  • delay the absorption of injected antigens, increasing their concentration at the local injection site
  • activate immune cells, producing an anti-inflammatory response

Generally, there are no specific precautions to consider before getting the hepatitis A vaccine.

However, some people may be allergic to certain ingredients in the vaccine. An allergic reaction can lead to anaphylaxis.

Healthcare professionals typically administer the hepatitis vaccine directly into muscle.

Adults and children require at least two doses of hepatitis vaccine to receive full immunity from the virus.

The CDC recommends the following vaccination schedule:

Children under 2 years:

  • First dose: 12 through 23 months of age.
  • Second dose: At least 6 months after the first dose.

Older children, adolescents, and adults should receive a second dose at least 6 months after the first.

Generally, there are no known safety concerns regarding the hepatitis A vaccine.

However, some people may be allergic to ingredients in the vaccine.

A person with a previous allergic history to the vaccine should consult a healthcare professional before receiving a second dose.

Possible side effects of the hepatitis A vaccine can range from mild to severe.

Mild adverse effects of the vaccine include:

  • injection-site reactions
  • skin rash
  • fever
  • headaches

Other rare side effects include:

The following are some questions people often ask about the hepatitis A vaccine.

How long is a Hep A vaccine good for?

Generally, people who have received two doses of the hepatitis A vaccine have lifelong immunity against the hepatitis A virus. However, some people may require booster doses.

How often is Hep A vaccine needed?

Hepatitis A vaccination typically requires one immunization series that includes two doses with a 6-month interval between the two.

How long after receiving the hepatitis A vaccine can a person travel?

Experts recommend getting vaccinated for hepatitis A as soon as possible after planning travel that requires it. This is because it can take up to 4 weeks after vaccination for antibodies against hep A to form.

The hepatitis A vaccine protects children and adults against a viral hepatitis A infection.

People require at least two doses of the hepatitis A vaccine to get lasting immunity against the virus. It is safe for most individuals. However, some people may develop an allergic reaction after receiving the vaccine.