Hepatitis B virus (HBV) infection is a major public health problem worldwide. Approximately 30% of the world’s population, or about 2 billion persons, have serologic evidence of current or past HBV infection. Of these, an estimated 360 million have chronic HBV infection and 600,000 persons die each year from HBV-related acute hepatitis, hepatocellular carcinoma (HCC, a form of liver cancer) and cirrhosis

 In accordance with its mandate to provide guidance to Member States on health policy matters, WHO issues a series of regularly updated position papers on vaccines and combinations of vaccines against diseases that have an international public health impact.

 Millions of people are living with viral hepatitis and millions more are at risk. Most people who were infected long ago with HBV or HCV are unaware of their chronic infection. They are at high risk of developing severe chronic liver disease and can unknowingly transmit the infection to other people.

Increased access to highly effective direct-acting antivirals (DAAs) for the treatment of infection with the hepatitis C virus (HCV) is revolutionizing the prospect of ending HCV epidemics. Globally, the number of people who initiated DAA-based treatment for HCV rose between 2015 and 2016, from approximately 1 million to 1.5 million.

 Hepatitis A virus (HAV) is a member of the Hepatovirus genus of the family Picornaviridae, and is a nonenveloped single-stranded RNA virus [Cuthbert, 2001; Koff, 1998]. HAV replicates in hepatocytes (liver cells) and interferes with liver function, sparking an immune response that causes liver inflammation.

 Hepatitis E virus (HEV) is a small, non-enveloped virus, approximately 27-34 nm in diameter. The virus has a polyadenylated, single-stranded RNA genome, approximately 7.2 kilobases in length, with a positive polarity and a cap at its 5’-end.