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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.

Term of the Week

Hot zone

A hot zone is a section of a facility (sometimes an entire facility or even a city district) where there is a high risk of contamination by patients with an infectious disease. All individuals entering a hot zone must respect appropriate protective measures. By analogy, “cold zone” and “warm zone” are used to refer to areas where there is no infected individual or only individuals suspected of having an infection.