Hepatitis B is a type of liver inflammation due to a viral infection. Healthcare organizations indicate that receiving the hepatitis B vaccine more than once is not harmful.

Hepatitis B can damage and reduce function in the liver. It can become a lifelong illness in some people.

This article explores hepatitis B vaccine safety, including booster doses, potential side effects, and benefits. It also discusses when someone should consider speaking with a healthcare professional.

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There are currently seven hepatitis B vaccines available in the United States. The vaccine comes in three doses.

An extra dose of a hepatitis B vaccine is safe to receive. It is not harmful.

Most people with healthy immune systems can get enough protection from a single course of vaccine shots. A doctor can administer a blood test to check a person’s immunity to the hepatitis B virus (HBV). This can help them decide whether a booster dose is necessary.

Some people may need a booster shot of a hepatitis B vaccine to help its effects last longer or ensure it provides extra protection.

Can an accidental extra dose of a vaccine cause health problems?

Some people accidentally receive an extra dose of a vaccine.

A 2019 study investigated 366,815 reports on all vaccines from the national Vaccine Adverse Event Reporting System. Researchers found that in 1.4% of the reports, people received an extra dose of a vaccine due to an administrative error.

In 76.9% of these instances, the reports did not suggest recipients of the doses experienced side effects.

The remaining reports had no unexpected or unusual side effects due to the extra dose.

The hepatitis B vaccine schedule

The hepatitis B vaccine comes in three doses. Children can receive the vaccine from birth, with the schedule as follows:

  • First dose: around the time of birth
  • Second dose: 1–2 months after birth
  • Third dose: around 6–18 months old

Adults can also receive the vaccine. They receive the second dose 1 month after the first, and the third dose 6 months after the second.

Older children up to 19 years old who have not received the vaccine should get it. They receive the doses in a similar schedule to adults.

Learn more about when people should get the hepatitis B vaccine.

As with any vaccine, getting the hepatitis B vaccine can cause side effects in some people.


Most vaccine side effects are mild. They usually pass within 1–2 days.

According to the University of Oxford, around 1 in every 10 people experience mild side effects after vaccination.

Side effects may include:


Around 1 in every 100 people experience some of the following adverse effects after vaccination:


About 1 in every 1,000 people experience more serious side effects after vaccination, such as:

People who experience these side effects should speak with a doctor. In extremely rare cases, a severe allergic reaction called anaphylaxis can occur. It is a medical emergency.

Anaphylaxis: Symptoms and what to do

Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:

  • hives
  • swelling of the face or mouth
  • wheezing
  • fast, shallow breathing
  • a fast heart rate
  • clammy skin
  • anxiety or confusion
  • dizziness
  • vomiting
  • blue or white lips
  • fainting or loss of consciousness

If someone has these symptoms:

  1. Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
  2. Dial 911 or the number of the nearest emergency department.
  3. Lay the person down from a standing position. If they have vomited, turn them onto their side.
  4. Stay with them until the emergency services arrive.

Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.

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According to the Department of Health and Human Services, the hepatitis B vaccine provides over 90% protection against HBV.

Acute, or short-term, HBV infections can become chronic, or long-term. The risk of developing a chronic HBV infection is higher when a person contracts the virus at a young age.

However, hepatitis B vaccines provide long-term protection. According to the Centers for Disease Control and Prevention (CDC), hepatitis B vaccines can have an effect for 30 years if a person receives them before 6 months of age.

People with hepatitis B, especially those under 30 years old, do not always have symptoms.

The CDC notes that hepatitis B causes premature death due to cirrhosis or liver cancer in 25% of people who develop a chronic infection during childhood and 15% of those who contract an infection after childhood.

Hepatitis B can remain asymptomatic until cirrhosis or cancer develops. This means vaccines are vital for reducing the risk of serious disease.

However, extra doses will not provide any extra benefits for people who already have enough protection from a single round of hepatitis B vaccine doses.

Some people may be hesitant about receiving any vaccine despite the safety and effectiveness of vaccines, including the hepatitis B vaccine.

They can discuss their concerns with a doctor or other qualified healthcare professional who can give vaccine recommendations for an individual’s age group and provide more information about vaccine safety.

Hepatitis B vaccines might not be safe for certain groups of people, including:

  • people who had an allergic reaction to a previous dose or any ingredients of hepatitis B vaccines
  • people with a yeast allergy
  • people who have experienced an allergic reaction to neomycin, an ingredient in a combined hepatitis A and hepatitis B vaccine called Twinrix

People who have been moderately or severely ill should speak with their doctor about when it would be safe to receive the hepatitis B vaccine following recovery.

It is safe for people to receive an extra dose of the hepatitis B vaccine. However, healthcare professionals do not recommend this to people unless they have low immunity to the virus after a single course.

Rarely, a person may receive an accidental extra dose. Evidence suggests the risk of side effects remains low and that the extra dose does not make side effects any more severe.

Vaccines are central to preventing hepatitis B. Severe side effects are very rare.

People may benefit from talking with a qualified healthcare professional about their hepatitis B immune status, whether they are protected, and what they can do next.