What does the appearance of anti-HBs indicate in hepatitis B infection?

The appearance of anti-HBs, or antibodies to Hepatitis B surface antigen, indicates that a person has either recovered from an acute Hepatitis B infection or has been vaccinated against the virus, leading to immunity. In the context of Hepatitis B, anti-HBs is a protective antibody that develops after the clearance of the virus.

This antibody typically appears after the resolution of the infection, when the body has effectively fought off the virus, and serves as a marker of immunity. Thus, the presence of anti-HBs implies that the individual is at a lower risk of being infectious and has a good immune response against future infections with Hepatitis B.

In the context of other options, the manifestation of anti-HBs does not correlate with acute infection, where one would expect to find Hepatitis B surface antigen (HBsAg) instead. Similarly, during a chronic Hepatitis B infection, there is usually persistent HBsAg, and anti-HBs would not be present. The term secondary infection does not accurately describe the presence of anti-HBs, as this antibody indicates recovery rather than concurrent or subsequent infections with the virus. Therefore, the presence of anti-HBs is clearly indicative of recovery and immunity from Hepatitis B.