Natural history of hepatitis B virus infection: pediatric perspective.

Hepatitis B virus (HBV) infection is an important disease globally. Chronic HBV infection may result in serious complications. Its transmission may be either perinatal or horizontal. Perinatal transmission is particularly important after the implementation of a universal vaccination program. Through either route, chronic carrier status is usually established in early childhood. The course of the disease course is determined by the host-virus interaction. The host's immune system initially tolerates the virus, and then gradually attempts to clear it. The virus, on the other hand, tries to avoid host immune system attack by a strategy involving targeted epitope mutations. By generating mutants, the virus can survive attacks from the host's immune system, enabling the infection to persist. Different individuals have different responses to HBV infection; genetic polymorphisms in cytokines, hormones, and other immune modulators may affect the final outcome of chronic HBV infection. Due to the implementation of a universal infant HBV vaccination program, HBV infection is now under control. Unfortunately, there still are some cases of vaccination failure. Very high maternal viremia, in utero infection, or escape mutants are possible reasons for vaccination failure. Immunocompromised hosts also risk vaccination failure. Blood or organ donors with occult HBV infection are possible sources for immunocompromised hosts. These victims of vaccination failure may exhibit a different disease course due to chronic HBV infection from those who acquired the infection before the universal vaccination era. The achievement of our ultimate goal of HBV elimination depends on a globally effective universal vaccination program, as well as the application of some novel successful medications to control those who are already infected.