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What is hepatitis B?

man grasping his his liverHepatitis B is the most common serious liver infection in the world. It is a virus that specifically attacks cells in the liver. Globally, there are nearly 300 million people living with chronic hepatitis B. Additionally, it has been estimated that about 2 billion people have been infected with hepatitis B (either acute or chronic). There are other viruses that may attack the liver such as hepatitis A, C, D and E, but each virus is unique. Fortunately, there is a vaccine to prevent new hepatitis B infections and excellent treatments for those that need treatment.

Hepatitis B can result in either an acute or chronic infection. When a person is newly infected, it is called an “acute” infection. If the person continues to test positive for hepatitis B surface antigen (HBsAg) for longer than 6 months, then it is considered a chronic infection. Testing is the only way to know for sure if a person is infected with hepatitis B, and if they have acute or chronic infection.

Babies and young children are particularly vulnerable to the hepatitis B virus. While ninety percent (90%) of babies and up to 50% of young children will progress to chronic infection with hepatitis B, only up to 10 percent (10%) of healthy adults will progress to chronic infection. (90% of healthy adults will clear acute hepatitis B infections. Most do not require any medication to clear an acute infection.).

People are often surprised to learn of their hepatitis B infection because there may be few or no symptoms for decades. They may think they have an acute hepatitis B infection, when, in fact, they were infected as a baby or young child and have a chronic infection. This is because hepatitis B may go unnoticed with no – or few mild – symptoms.

The good news is that hepatitis B can be prevented with the safe and effective hepatitis B vaccine. Ideally, ALL babies are vaccinated within 24 hours of birth and complete the vaccine series on schedule, to protect them from hepatitis B for a lifetime.

Learn more about the science behind hepatitis B in this short video by Dr. Thomas Tu: 


Find more Frequently Asked Questions here


Page updated 02/09/2022