Hepatitis B

What is hepatitis B?

Hepatitis B is a liver disease caused by the hepatitis B virus (HBV). Since 1991 when children started getting vaccinated for the virus, cases of hepatitis B in the U.S. have gone down 82 percent, according to the Centers for Disease Control.

HBV spreads through blood, saliva or other bodily fluids. The most common way children become infected with hepatitis B is if they are born to a mother with the virus. Older children can become infected through injection drug use or unprotected sex.

There are two phases of hepatitis B — acute and chronic.

Acute hepatitis B is often a mild illness that most often clears on its own in a matter of weeks. Children and adults who are not able to clear an HBV infection within six months go on to develop chronic hepatitis B.

Chronic hepatitis B is a serious illness that can cause long-term health problems. The risk that a child with acute hepatitis B will develop the chronic form goes down with age. An infant with acute hepatitis B has about a 90 percent chance of developing chronic infection; the risk in children under five years old is about 30 percent, while that of an adult is between six and ten percent.

Over the course of decades, chronic hepatitis B progresses through four stages — immune tolerance, immune clearance, inactive carrier, and reactivated — based on the behavior of the virus and how the child's immune system responds against it. The inactive carrier phase can last for years, often until well into adulthood.

What is the liver, and what does it do?

The liver is the second largest organ in the body, located in the abdominal cavity. The liver helps the body in many ways:

  • the liver produces proteins that allow blood to clot normally, transport oxygen and support the immune system
  • it produces bile, a substance that helps digest food
  • it stores extra nutrients
  • it helps clean the bloodstream of harmful substances
  • it helps control blood sugar and cholesterol levels

How does hepatitis B affect the liver?

In acute symptomatic hepatitis B, the liver can become swollen and inflamed, however the infection is often silent, particularly in infants. If the infection becomes chronic, the virus can cause inflammation and cause the healthy, soft tissues of the liver to harden and scar. About a quarter of people with chronic hepatitis B develop serious liver diseases such as cirrhosis or liver cancer as adults.

What is the difference between hepatitis B and hepatitis C?

Hepatitis B and hepatitis C are caused by different viruses. Other differences include:

More children and adults are infected with hepatitis C.

  • There are an estimated 19,000 new hepatitis B infections a year.
  • There are an estimated 30,000 new hepatitis C infections a year.

The rate of mother-to-child infections is higher with hepatitis B.

  • According to the World Health Organization, a mother with hepatitis B has up to a 90 percent chance of passing the virus to her child while giving birth.
  • A mother with hepatitis C has about a 5 percent (1 in 20) chance of passing the virus to her child while giving birth.

There is a vaccine for hepatitis B.

  • A child born to a mother with hepatitis B should receive the vaccine within 12 hours after birth. This will be the first of three doses.
  • There is currently no vaccine for hepatitis C.

The risk for chronic infection is higher for young, unvaccinated children with hepatitis B, but the risk goes down as children get older.

  • Younger children who have not been vaccinated are at the highest risk of developing chronic hepatitis B. Among unvaccinated children, 90 percent of babies, 20-50 percent of toddlers aged 1-5 years old and 6-10 percent of older children progress from acute to chronic hepatitis B.
  • Between 20 and 30 percent of children and adults with acute hepatitis C develop chronic hepatitis C.

Despite all of the differences, hepatitis B and hepatitis C are also similar in many ways.

  • The viruses that cause them spread when the blood of someone infected with the virus enters the body of another person.
  • Neither virus is spread by hugging, kissing, coughing or sneezing.
  • Both start with an acute stage and sometimes progress to a chronic stage.
  • A child's immune system can often clear the body of either virus without medication.
  • If either virus progresses to the chronic stage, the child may develop cirrhosis or liver cancer as an adult.

How we care for hepatitis B

The Center for Childhood Liver Disease at Boston Children's Hospital is one of the leading centers in the world for the care of children with hepatitis B. The center’s director, Maureen Jonas, MD is a national leader in the care, diagnosis and treatment for children with hepatitis. Dr. Jonas, along with her team, wrote the clinical guidelines that shape the way pediatric GI specialists and pediatricians around the country treat hepatitis B.

In addition to the standard treatments, our team of certified pediatric hepatologists is also at the forefront of treatment research, actively working to help make newly approved treatments for adults with hepatitis C available to children.

Our areas of innovation for hepatitis B

Liver biopsies provide a great deal of information about the extent of damage in a child’s liver, but the procedure is invasive and can be both painful and risky. Researchers at Boston Children’s are investigating an ultrasound-based imaging technology called Fibroscan that may be able to help doctors assess liver scarring through a virtual biopsy.