What indicates immunity in Hepatitis B?

The presence of Anti-HBs (antibody to hepatitis B surface antigen) is the key indicator of immunity in Hepatitis B. When someone has been vaccinated against Hepatitis B or has recovered from an acute infection, they develop these antibodies. The presence of Anti-HBs indicates that a person has either immunity from vaccination or has cleared an infection, providing protective immunity against future infections.

In the context of immunology, Anti-HBs is associated with the resolution of the infection and the body's adaptive immune response. It is important in determining a person's immune status, as the presence of these antibodies typically signifies a successful immunization or infection resolution, rather than active disease.

Other markers, such as HBsAg, indicate active infection, while Anti-HBc signifies past infection or exposure, but does not confirm the status of immunity. Positive Anti-HCV is associated with a different virus, Hepatitis C, and does not provide any information regarding Hepatitis B immunity. Thus, Anti-HBs is the definitive marker of immunity against Hepatitis B.