The hepatitis B vaccine is a safe and effective way to prevent infection with the hepatitis B virus (HBV). It is an inactivated virus, so the risk to the fetus is very low. There is also no evidence of any risks from vaccinating against HBV during pregnancy or nursing.

Hepatitis B is an infection of the liver that occurs due to HBV. Some forms can be chronic and could lead to cirrhosis and liver cancer. Cirrhosis refers to scar tissue building up in the liver.

If a pregnant person develops HBV, the virus can pass from them to the baby during or after birth. If a baby gets hepatitis B, there is a 90% chance they will develop a lifelong infection.

Hepatitis B vaccines can reduce the risk of a person developing HBV and complications from the virus in both the pregnant person and the fetus.

The American College of Obstetricians and Gynecologists recommends immunization for pregnant people and explains that there are no known risks of vaccinating against HBV during pregnancy.

Additionally, a pregnant person who gets vaccinated against the virus should not expect it to cause problems that would require any extra monitoring of the fetus.

This article looks at the HBV vaccine during pregnancy, the side effects and risks, frequently asked questions, and more.

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The hepatitis B vaccine is safe to take during pregnancy. However, a pregnant person who receives the vaccine during pregnancy should be aware that the fetus also will need the vaccination after birth.

This is because the protective antibodies do not transmit from the pregnant person to the fetus.

The United States Preventive Services Taskforce recommends that every pregnant person who receives prenatal care should undergo screening for HBV.

Screening for the virus can help healthcare professionals and pregnant people identify if they are at risk of contracting HBV, so they can protect the fetus from infection.

If a fetus gets hepatitis B, it can lead to severe and potentially deadly health complications without treatment.

Each hepatitis B vaccine contains a protein from the HBV virus. However, the vaccine is inactive, meaning the protein from the virus is dead.

This means the vaccine cannot cause the virus and does not have a negative effect on the pregnant individual or developing fetus.

Most of the ingredients in vaccines already occur naturally in a person’s body or the food we eat. The main ingredients within the drug include the following:

  • aluminum
  • yeast proteins
  • formaldehyde
  • sodium chloride
  • sodium borate

The hepatitis B vaccine causes common side effects in around 1 in 10 people who have it. For pregnant individuals, the most common side effects, according to a 2014 study, include discomfort around the injection site and mild to moderate fever.

Uncommon side effects include:

Most side effects are mild and will go away on their own. However, an individual should consult a doctor as soon as possible if uncommon or rare side effects occur.

Here are some common FAQs about getting the hepatitis B vaccine and other vaccinations during pregnancy:

Do you need a hep B vaccine when pregnant?

A person should ideally receive an HBV vaccination before pregnancy. However, it is safe to receive it during pregnancy as well.

Individuals should receive the vaccination, as HBV can spread from parent to child. It transmits through contact with the blood or body fluids of those with hepatitis B.

For babies, the most common transmission method is when a pregnant person who has hepatitis B passes the virus to the fetus during birth.

This can result in severe disease for the parent and chronic infection for the baby.

The Centers for Disease Control and Prevention (CDC) recommends an HBV vaccine for all infants, children, and adults in the United States. If a person did not receive the HBV vaccine as an infant, then it is recommended for children and adolescents.

Adults should discuss vaccinations with healthcare professionals. Vaccine recommendations vary depending on age and risk factors.

People with an increased risk for HBV, including healthcare workers, people with STIs, those who use drugs intravenously, and individuals with chronic liver disease, should also receive HBV vaccination.

For infants, healthcare professionals administer:

  • the first dose at birth
  • the second dose when a baby is 1–2 months of age
  • a third dose when they are 6–18 months

What happens if the hep B vaccine is not given at birth?

All babies should receive a vaccination to protect them against hepatitis B infection. If they get contracts HBV, there is a high chance they will develop a lifelong infection.

Without treatment, hepatitis B in babies can lead to severe and potentially deadly health complications. Hepatitis B can also have a number of serious effects on the liver or even death from cirrhosis or liver cancer.

What vaccines cannot be given during pregnancy?

Doctors do not recommend some vaccines during pregnancy, such as:

If a person finds out they are pregnant after having any of the vaccines above, they should talk with a doctor.

A healthcare professional should administer further doses of the vaccines to the individual after birth if necessary.

Through prenatal care and blood testing, a pregnant person can find out if they are at risk for transmitting hepatitis B to a fetus.

Treatments and vaccines can help prevent babies from having lifelong infections that could increase their risk for early death.

If a person is pregnant, they should talk with their doctor about ways to protect themselves and their fetus from hepatitis B.