Recently, I have been asked by many patients: Can a father with hepatitis B pass it on to his children? How contagious is it? How to prevent it? The answers are as follows: 1. Can it be transmitted? Yes. (1) We can see clinically that the father is hepatitis B positive, the mother is hepatitis B negative, and the children are hepatitis B positive. (2) The sperm of a hepatitis B-positive person can indeed carry hepatitis B virus nucleic acid (HBV DNA), which is the most infectious. (3) The sequence (order of nucleotide arrangement) of the father’s hepatitis B virus nucleic acid is basically the same as that of the child’s hepatitis B virus nucleic acid, and even the loci where it mutates are the same. This is a good indication that the hepatitis B virus of his children is derived from his father. 2. How infectious is it? I don’t know. But it does seem to be much less likely than mother-to-child transmission. Why don’t we know? This is because it is very difficult to determine if the transmission is from father to child, and the diagnosis cannot be made solely on the basis of the fact that the father is hepatitis B positive, the mother is hepatitis B negative, and the child is hepatitis B positive. The sequencing of hepatitis B virus nucleic acid is so expensive that hospitals generally do not do it. Therefore, there is no material available for this purpose. 3. How to prevent it? There is no material in this area at home or abroad. According to the materials I have and my reasoning, I would like to present some of my personal views for your reference. If a hepatitis B male is negative for hepatitis B virus nucleic acid in his blood, he will not infect his child and can be left untreated. If you are currently taking antiviral drugs and the hepatitis B virus nucleic acid negative, then you should switch to telbivudine or tenofovir (lamivudine can also be) 1-2 months after the hepatitis B virus nucleic acid continues to be negative, you can also have children. If the hepatitis B virus nucleic acid is positive, especially when the titer is high (>105 copies/ml), you should use antiviral drugs (tenbivudine or tenofovir, lamivudine can also be used) until the hepatitis B virus nucleic acid turns negative and then use it for 4 months, if the hepatitis B virus nucleic acid is still negative, then you can have children. This is because the life span of sperm is usually 100 days, so if you use it for 4 months after the hepatitis B virus nucleic acid has turned negative, the infected sperm will have died out, and the newborn sperm will not be infected again because the hepatitis B virus nucleic acid has turned negative. So this time to have children will not be infected. 4. So are these 3 antiviral drugs likely to have a negative effect on sperm? Although there is a lack of direct evidence, it seems that there may be no effect from the use of drugs on mother-to-child transmission, it must be stressed that normal pregnancy, without any drugs, has a 1-2% teratogenic rate in newborns. Therefore, in case of malformations in the newborn, it cannot be said that they are caused by drugs.