[Is it necessary to revaccinate against hepatitis B virus when the titer of anti-HBs drops below 10 IU/L?]

Viral hepatitis B still represents a major epidemiological issue worldwide. After recombinant vaccine administration, a titer of anti-HBs antibodies ≥ 10 IU/L has long been considered to be seroprotective. Persons without this antibody level after complete vaccination are referred to as non-responders. A progressive decline in anti-HBs levels over years is also commonly seen in responders. Recently, there has been increasing evidence that the titer of anti-HBs ≥ 10 IU/L does not provide 100 % protection against infection and clinically manifest illness. Additionally, an important role of cellular immune memory has been demonstrated - without any correlation with anti-HBs titer. Based on current knowledge, there is no need for regular anti-HBs titer testing or booster vaccination in immunocompetent individuals with anti-HBs ≤ 10 IU/L. At present, regular serological testing and, if need be, revaccination to maintain anti-HBs ≥ 10 IU/L are recommended in immunocompromised persons and after liver transplantation.