The vast majority of infants infected with hepatitis B have no symptoms, because hepatitis B infection in infants is transmitted from mother to child. Infants with defective immune systems or due to associated immune tolerance do not show signs of significant liver damage when infected with the hepatitis B virus. The state exhibited by the infant at this time is immune tolerance, and there will be no manifestation of liver damage because the immune system does not clear the liver cells infected by the hepatitis B virus. If they grow into adolescents or adults, at some point they may enter immune clearance before liver cell damage occurs with corresponding clinical symptoms. However, some infants infected with the hepatitis B virus may also develop infantile hepatitis syndrome, which is a phenomenon that can be seen before the hepatitis B vaccine is commonly administered. Infantile hepatitis syndrome, if more severe, is likely to affect the life of the infant.