What does the Hep B antibody to core antigen indicate?

The presence of antibodies to the core antigen of Hepatitis B virus (anti-HBc) indicates exposure to the virus, but it is particularly relevant in distinguishing between acute and chronic hepatitis B infections. When someone presents with symptomatic hepatitis B, particularly in the acute phase of the disease, they will have detectable levels of anti-HBc, as this antibody is produced in response to active viral replication during infection.

Specifically, in acute infections, both IgM and IgG variants of anti-HBc can be present, with IgM anti-HBc indicating a recent infection that has occurred within the last six months. This helps healthcare providers determine that the patient is currently experiencing an acute hepatitis B infection, as opposed to having had an earlier or chronic infection.

In contrast, individuals who are vaccinated against hepatitis B will generally have antibodies to the surface antigen (anti-HBs) but will not have anti-HBc unless they have encountered the virus. Thus, the presence of anti-HBc alone is not indicative of vaccination or chronic infection without additional context, which confirms that the answer linking anti-HBc to acute infection is accurate.