Assays for hepatitis B surface antigen (HBsAg) are the most frequently used tests to detect HBV infection. Vaccination for HBV can produce transiently detectable levels of HBsAg in patients.

Health secretary Robert F. Kennedy Jr. has expressed another unorthodox view on vaccines, declaring that single antigen ...

Many pathogens evade the host's immune response by periodically changing their surface antigens so that existing antibodies no longer recognize them. "This strategy is known as antigenic variation ...

The immune system responds to an infection by producing antibodies that recognize and bind to the cell surface of the pathogen, thus marking it as an intruder and triggering an immune response.