Hepatitis B is a DNA virus. It is transmitted by direct contact with blood or bodily fluids from an infected person.
Hepatitis B can be passed from mother to child around delivery, called vertical transmission. It can also be passed through sharing household products contaminated with blood, such as toothbrushes, contact between minor cuts or abrasions, or other high-risk activities such as sexual intercourse or sharing needles. It is not spread by casual contact, such as ordinary hugging, kissing (without mouth sores or bleeding gums), sharing food or coughing.
Most older children and adolescents clear acute infection within several months. However, a portion develops chronic hepatitis B infection. In chronic infection, the virus persists in liver cells, with ongoing viral replication and production of viral proteins. The risk of developing chronic hepatitis B after exposure is:
- Around 90% for neonates
- Around 30% for young children
- Under 10% for older children and adolescents
Most children with chronic hepatitis B are asymptomatic, with normal growth and development and normal liver function tests. A small minority develop cirrhosis or hepatocellular carcinoma during childhood. These risks increase once they enter adulthood.
Vaccination involves injecting the hepatitis B surface antigen. In the current UK schedule, children receive the hepatitis B vaccine as part of the 6-in-1 vaccine at 8, 12 and 16 weeks, with a fourth dose at 18 months for children born on or after 1 July 2024.
Viral Markers
Antibodies are produced by the immune system against pathogen proteins. Antigens are molecules recognised by the immune system. Antibodies are part of the immune system. In hepatitis B, antigens are viral proteins. There are five key viral markers to understand and remember with hepatitis B:
- Surface antigen (HBsAg) – active infection
- E antigen (HBeAg) – a marker of viral replication and implies high infectivity
- Core antibody (HBcAb) – implies past or current infection
- Surface antibody (HBsAb) – implies vaccination or past infection
- Hepatitis B virus DNA (HBV DNA) – a direct count of the viral load
Testing usually includes HBsAg, HBcAb and HBsAb, depending on the clinical context. Antenatal screening involves testing pregnant women for HBsAg. When positive, further testing is performed for HBeAg and viral load (HBV DNA).
HBsAb demonstrates an immune response to HBsAg. The HBsAg is given in the vaccine. A positive HBsAb may indicate they have been vaccinated and have an immune response to the vaccine. HBsAb may also be present following a past infection.
HBcAb can help distinguish acute, chronic and past infections. We can measure IgM and IgG versions of HBcAb. IgM suggests recent acute infection, but can also appear during flares of chronic hepatitis B. IgG indicates previous exposure to the hepatitis B virus and persists long term.
HBeAg correlates with infectivity. HBeAg indicates active viral replication and high infectivity, and may be present in acute or chronic infection. When the HBeAg is positive, they are highly infectious to others. In chronic hepatitis B, active viral replication can occur even when HBeAg is negative, so HBV DNA is needed to assess viral load. HBeAb usually indicates lower infectivity.
Hepatitis B Positive Mothers
All women are offered screening for hepatitis B during pregnancy. A neonatal alert will be set up for women who are positive for hepatitis B, so that everything is in place, ready for birth.
To reduce the risk of the baby contracting hepatitis B, neonates with hepatitis B positive mothers are given both:
- Hepatitis B vaccine (given within 24 hours of birth and at 4 weeks, in addition to the normal vaccination schedule)
- Hepatitis B immunoglobulin (given within 24 hours of birth if the mother is considered highly infectious)
Children born to hepatitis B positive mothers are tested for HBsAg at 12 months of age.
The hepatitis B virus can be found in the breast milk of mothers with hepatitis B. However, breastfeeding is considered safe, provided the infant has been vaccinated according to schedule.
Management
Most children with chronic hepatitis B are asymptomatic and do not require treatment. They require regular specialist follow-up for monitoring (e.g., ALT, HBV DNA and HBeAg). Where there is evidence of hepatitis or liver fibrosis, treatment with antiviral medications may be considered.
Last updated May 2026
Now, head over to members.zerotofinals.com and test your knowledge of this content. Testing yourself helps identify what you missed and strengthens your understanding and retention.
