Hepatitis B virus
Breakthrough cases of Hepatitis B are primarily attributed to mutations in the Hepatitis B virus (HBV) that make HBV surface proteins unrecognizable to antibodies produced from the HBV vaccine. Viruses with such mutations are called “vaccine escape mutants”. Breakthrough infections may also be caused by delayed vaccination, immunosuppression, and maternal viral load. It is possible for an individual to have breakthrough infection of HBV but be asymptomatic.