What does the presence of anti-HBs indicate in a Hepatitis B screening?

The presence of anti-HBs (antibodies to hepatitis B surface antigen) indicates vaccine immunity. This occurs when an individual has been successfully vaccinated against hepatitis B, leading to the production of these antibodies in response to the vaccine. The presence of anti-HBs is a sign that the immune system recognizes the hepatitis B virus and can mount a defense against it if exposed in the future.

It's important to differentiate this from other potential scenarios, such as acute or chronic infections, where different markers would be present. In acute infections, one would typically find the hepatitis B surface antigen (HBsAg), indicating an ongoing infection, while in chronic infections, both HBsAg and anti-HBc (antibodies to hepatitis B core antigen) would be present. Natural immunity, which may occur after recovering from a hepatitis B infection, would also show anti-HBs presence alongside other markers but is more complex as it involves other antibodies and antigens related to the core and surface of the virus.