1. Initially linked to long incubation (average of roughly 100 days), hepatitis B can be spread by serum (homologous serum hepatitis) or blood component transfusion (not gamma globulin). Subsequently it has been observed that the most common forms of transmission are related to perinatal spread (from mother to neonate at time of delivery) and sexual spread (especially homosexual).
2. The hepatitis B virus is the only human virus that is routinely tested for by measuring a marker, or “footprint,” of the virus in the blood. The hepatitis B surface antigen (HBsAg) is produced in remarkably large quantities and almost all of it is noninfectious protein.
3. The infection causes acute hepatitis, which can be asymptomatic, anicteric, icteric or fulminant, and it can lead to chronic hepatitis. Some cases of chronic hepatitis B can result in hepatocellular carcinoma.
4. The vaccine to prevent this viral infection was licensed for use in 1982 and has made a major difference in the spread of the virus. The vaccine—now a preparation of HBsAg produced in a recombinant yeast—is one of the earliest given in a neonate’s life and is part of routine childhood immunization in the developed world. Because the vaccine prevents an infection that may result in cancer, it should be acknowledged as the first cancer vaccine.
5. The vaccine’s protection against the infection lasts longer than the antibody to the HBsAg. At this point, routine reimmunization for individuals is not recommended.
Active infection with hepatitis B is needed to support another hepatitis virus, the delta virus also called hepatitis D. This virus, with a very small RNA genome, requires HBsAg to encapsulate itself.
Bhattacharya D, Thio CL. Review of hepatitis B therapeutics. Clin Infect Dis. 2010;51:1201-1208.
Zanetti AR, Mariano A, Romano L, et al. Long-term immunogenicity of hepatits B vaccination and policy for booster: an Italian multicentre study. Lancet. 2005;366:1379-1384.