Hepatitis B carriers are not contagious when they test for hepatitis B virus DNA quantification of 0. Hepatitis B carriers are generally contagious, if the viral load of hepatitis B carriers is undetectable, that is, the DNA assay test result value is 0, indicating that it is not contagious. Hepatitis B carriers are people with normal liver function and no histologic or biochemical abnormalities, and the condition of such people is relatively stable. However, it does not mean that there is no replication of hepatitis B virus, basically in the stage of immune tolerance, most of them are infectious. It is important to pay attention to the prevention of hepatitis B. The disease is mainly transmitted through blood, mother-to-child vertical transmission and sexual contact. People who don’t have hepatitis B surface antibody can get hepatitis B vaccine to prevent it.