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Hepatitis B is a double stranded DNA virus that causes liver inflammation (acute and/or chronic hepatitis). In people with chronic infection around 25% will develop cirrhosis that progresses to end stage liver disease  and there is a 200-fold increase in risk of hepatocellular carcinoma (HCC)  . Adults with chronic hepatitis B infection acquired in childhood develop HCC at a rate of 5% per decade .
Hepatitis B may be transmitted vertically (from mother to child) or horizontally by exposure to infected body fluids (blood or semen). Horizontal transmission is important in children < 5 years and household or sexual contacts of people with Hepatitis B infection .
The incubation period is 45 -160 days (mean of 90 days) [5, 6].
Clinical manifestations depend on the age at acquisition, viral load and host immune status. The virus itself is probably not cytopathogenic; most complications are the result of the host immune response attempting to destroy viral infected cells.
The risk of vertical transmission is dependent upon the maternal viral load. Women who are HBeAg positive have a 90% risk of transmission in the absence of immunoprophylaxis . Even in the presence of appropriate immunoprophylaxis, mothers with a high viral load (HBV DNA >200,000 IU (106 copies)/mL)) have a transmission risk of 8-30% .
In Australia, pregnant women are screened for Hepatitis B infection at their first antenatal visit.
Hepatitis B vaccination is part of the routine immunisation schedule in Australia (given at birth, 2, 4 and 6 months) and in many countries of origin for humanitarian entrants. Worldwide vaccination schedules are available.
The prevalence rate of hepatitis B infection is highest in South-East Asia and Sub-Saharan Africa . Recent studies in refugee cohorts in Australia suggest the prevalence of chronic hepatitis B infection is:
All children attending Immigrant health clinic are screened for:
A titre of HBsAb >10 IU/L indicates adequate immunity. If HBsAb is <10 IU/L, exclude infection, then give hepatitis B catch-up vaccination; see Immunisation Handbook
If children are HBsAg + they should have further tests to determine acute vs chronic infection and presence/absence eAg to give information about infectivity:
Screen for hepatitis A immunity (to determine if hepatitis A vaccination required) and consider risk factors and screening for HIV, HCV, and schistosomiasis in children with hepatitis B.
Treatment has been less well studied in children than adults, although it may be indicated in a few circumstances, such as the immune clearance phase, where there is evidence of liver damage on biopsy.