Hepatitis B surface antigen positive is a person infected with the hepatitis B virus, who is contagious. The size of infectiousness is determined by the level of hepatitis B virus quantitative level, the higher the level of hepatitis B virus quantitative level, the more infectious, the lower the level of hepatitis B virus quantitative level, the less infectious, hepatitis B surface antigen-positive patients after antiviral treatment, the viral load can get a control. If the examination of hepatitis B virus DNA has been reduced to negative, this time the infectiousness is very small. The most effective measure to prevent hepatitis B virus infection is to take the hepatitis B vaccine, through the vaccine can obtain hepatitis B surface antibody, liver surface antibody can be as high as 95% of the human body’s protective properties, so you do not have to worry about being infected with hepatitis B.