Premature infants with immature immune systems usually require 4 doses of hepatitis B. Premature infants who are HBsAg negative and have stable vital signs and a birth mass of ≥2000 g can receive hepatitis B vaccine according to the 3-dose vaccination protocol at 0, 1, and 6 months of age, preferably with a booster dose at 1-2 years of age; if vital signs are unstable, other diseases should be treated first, and then after stabilization If the vital signs are unstable, other diseases should be treated first and then vaccinated according to the above protocol. If the body mass of the premature infant is <2000g, the first dose of hepatitis B vaccine should be given after the body mass reaches 2000g (if the body mass does not reach 2000g before discharge from the hospital, the first dose should be given before discharge from the hospital); after 1 month, the 3-dose regimen of 0, 1, and 6 months should be repeated. Premature infants born to HBsAg-positive pregnant women must receive HBIG intramuscularly within 12 h after birth, regardless of their physical condition, and another injection is required after an interval of 3 to 4 weeks. If the neonate's vital signs are stable, there is no need to consider the body mass and the first vaccination should be given as soon as possible; if the vital signs are unstable, the first vaccination should be given as soon as possible after stabilization; after 1~2 months or after the body mass reaches 2000g, the neonate will be vaccinated again according to the 3-vaccination protocol for 0, 1 and 6 months