Hepatitis B is the abbreviation of chronic hepatitis B. It is an infectious disease caused by infection with the hepatitis B virus, and the main sources of infection are hepatitis B patients and HBV carriers. There is a characteristic of hepatitis B disease called familial aggregation, the cause of this phenomenon is not hepatitis B genetic, the main cause is mother-to-child transmission. Vertical transmission is caused by the fetus coming into contact with the blood of the HBV-positive mother during childbirth, and if the child is not vaccinated against hepatitis B in time, it is likely to become a carrier of the hepatitis B virus; while some fetuses are born to live closely with their HBV-positive mothers for a long time, this way of being infected becomes horizontal transmission, mostly due to close contact in the process of living together later in life. This route of transmission is called horizontal transmission, which is mostly caused by close contact during the process of living together later in life. At the same time, the transmission of hepatitis B is also sexually transmitted, so it may cause the whole family to suffer from hepatitis B. This is the family aggregation of hepatitis B. The prevention of hepatitis B should start from the fetus. At present, China has developed a vaccination program, and infants should be given hepatitis B vaccine and immunoglobulin in a timely manner after birth, while active and passive immunization methods can be adopted to deal with accidental contact with blood and body fluids of infected persons in a timely manner. In addition, it is important to develop good personal hygiene habits and avoid sharing household items with others.