A change in status from antigen positive/antibody negative to antigen negative/antibody positive; when an antigen is no longer detected in the blood, and the body produces antibodies to the antigen. It is a sign that the immune system has gained control of an infection. Seroconversion of hepatitis B surface antigen positive/surface antibody negative to surface antigen negative/surface antibody positive connotes being "cured" of a chronic HBV infection since the virus has been cleared from the liver and bloodstream.