Curriculum · Gastroenterology
Risk of chronic hepatitis B by age at infection
What it is
Whether an acute hepatitis B infection is left as chronic infection is decided by the age at which the virus is acquired, and the risk runs inversely with that age: the earlier in life the infection is acquired, the higher the risk of chronic HBV. About 90% of infants infected at birth go on to chronic infection. Of children infected between the ages of 1 and 5 years, 25% to 50% do so. In older children and adults the risk is only 1% to 5%.
Causes and risk
HBV is transmitted by exposure to the blood or body fluids of an infected person, including through injection drug use, sexual contact with an infected person, or transmission by an infected mother to her infant during delivery. Hepatitis B vaccine plus HBIG is indicated for postexposure prophylaxis after needle-stick injury and for sexual and household contacts of patients with HBV.