Many parents who have had their children tested for hepatitis B often ask, “How can my baby still have hepatitis B when he was born with the highly effective hepatitis B immune globulin and vaccine? Indeed, we often encounter children with hepatitis B who were born with hepatitis B immunoglobulin and vaccine, so why? Children born with high-valent hepatitis B immune globulin and vaccine are more than 90% protected, but not 100%, so less than 10% of children born to hepatitis B mothers will be infected with the hepatitis B virus. Can hepatitis B virus infection occur after the birth of a child? When the mother is infected with HBV genotype C, the child may be infected in utero, and hepatitis B immunoglobulin and vaccination after birth may not prevent hepatitis B virus infection. Second, with the mother is high viremia, the mother is high viremia, high HBsAg titer, if not treated, the child is born with a greater chance of infection with hepatitis B virus infection. Third, it is associated with vaginal delivery, low response to vaccine and the production of escape mutants from the vaccine. It is also related to the timing and dose of hepatitis B immunoglobulin injection, which is generally required as early as possible within 24 hours after birth, preferably within 2 hours after birth. If hepatitis B immunoglobulin is injected more than 24 hours after birth, then it will not achieve a good preventive effect. Because the hepatitis B virus in the child’s blood is not free at this time, the hepatitis B immunoglobulin will not neutralize the hepatitis B virus very well. If the amount of virus in the child’s blood is large and the amount of hepatitis B immunoglobulin injected is too small, it will not neutralize all of the hepatitis B virus, and the child may still have hepatitis B virus infection after the vaccination.