Anti-HBs is an antibody produced by the body against the surface antigens of the hepatitis B virus (HBsAg). The appearance of anti-HBs in the serum follows the disappearance of HBsAg. In most individuals, anti-HBs persists for life and provides long-term immunity. In some patients, however, there is a window during which neither HBsAg nor anti-HBs is measurable. This period may last several weeks or months. Other tests such as the anti-HBc IgM can be used during this window. In 5% to 30% of individuals, there is the simultaneous but abnormal presence of HBsAg and anti-HBs.
In these cases, it appears that the antibody is unable to neutralize the viruses in circulation. These individuals must be considered as HBV carriers (contagious).
Anti-HBs results are generally interpreted in light of other hepatitis B profile tests (HBsAg and, if necessary, anti-HBc antibodies, etc.).
A positive anti-HBs result is consistent with a previous HBV infection. A result ≥ 10 International Unit/Liter (≥ 10 IU/l) also appears between 1 and 6 months following a successful vaccination against hepatitis B. When negative (<10 IU/L]), the test can be used to identify individuals who are not protected against hepatitis B for vaccination/revaccination purposes.