What is the schedule for hepatitis B vaccine administration for infants who weigh less than 2000 grams?

Decreased seroconversion rates might occur among preterm infants with birth weights less than 2,000 grams after administration of HepB at birth. However, by the chronological age of 1 month, all preterm infants, regardless of initial birth weight, are likely to respond as adequately as larger infants. Infants who weigh less than 2,000 grams born to HBsAg-positive mothers and mothers with unknown HBsAg status (if the mother’s HBsAg status cannot be determined within 12 hours of birth) must receive immunoprophylaxis with HepB and hepatitis B immune globulin (HBIG) within 12 hours of birth. The initial vaccine dose should not be counted toward completion of the hepatitis B series, and 3 additional doses of HepB should be administered, beginning when the infant is age 1 month. Infants weighing less than 2,000 grams born to HBsAg-negative mothers should receive the first dose of the HepB series at hospital discharge or at chronological age 1 month (even if weight is still less than 2,000 grams), whichever comes first.