Hepatitis B virus infection, its sequelae, and prevention by vaccination.

Hepatitis B virus (HBV) infection is a global health problem. There are >350 million of people chronically infected with this virus worldwide. Hepatitis B vaccines are effective in preventing the infection. Humoral immunity is the key factor in conferring the protection. Hepatitis B surface antibody titers of ≥10mIU/mL are protective. Chronic carriage of HBV is related to the age when the infection occurs, the younger the age the higher the chronicity rate. Hence, vaccination should be given in early childhood. People vaccinated in infancy have a protection of >20 years, and hepatocellular carcinoma decreases in them. Although the vaccine-conferred immunity wanes by time, a universal booster is not recommended at present.