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  • Hepatitis B
  • Pregnancy, Perinatal & Infants

Please review the HepB vaccination recommendations for preterm infants who weigh less than 2,000 grams (4.4 pounds), as well as for those premature infants who weigh more.

Preterm infants weighing less than 2,000 grams (4.4 pounds) at birth have a decreased response to HepB administered before age 1 month. By age 1 month, medically stable preterm infants, regardless of initial birth weight or gestational age, have an immunologic response to HepB vaccination that is comparable to that of full-term infants. For preterm infants weighing less than 2,000 grams at birth:

  • If maternal HBsAg status is positive:
    • Give hepatitis B immune globulin (HBIG) plus HepB vaccine within 12 hours of birth. The birth dose (the initial HepB dose) should not be counted as part of the vaccine series.
    • Give 3 additional HepB doses (for a total of 4 doses) at ages 1, 2 to 3, and 6 months, or HepB-containing combination vaccine (Pediarix or Vaxelis) at ages 2, 4, and 6 months. The final dose should not be administered before 24 weeks of age.
    • Test for HBsAg and anti-HBs at age 9–12 months, or 1–2 months after the final dose of the vaccine series if completion of the series is delayed. Testing should not be performed before age 9 months (anti-HBs resulting from use of HBIG might still be positive and therefore misleading) or within 1 month of the most recent HepB dose (testing for HBsAg sooner than 1 month of a vaccine dose might produce a transient HBsAg-positivity).
  • If maternal HBsAg status is unknown:
    • If the mother’s HBsAg status cannot be determined within 12 hours of birth give HBIG plus HepB vaccine. The birth dose of vaccine should not be counted as part of the 3 doses required to complete the HepB series.
    • Three additional doses of vaccine (for a total of 4 doses) should be administered according to the recommended schedule on the basis of the mother’s HBsAg test result. The final dose in the series should not be administered before 24 weeks of age.
  • If it is not possible to determine the mother’s HBsAg status:
    • The vaccine series should be completed according to a recommended schedule for infants born to HBsAg positive mothers.
  • If the maternal HBsAg status is negative:
    • If you are certain that appropriate maternal testing was done and a copy of the mother’s original laboratory report indicating that she was HBsAg negative during this pregnancy is placed on the infant’s chart, delay the first dose of HepB vaccine until age 1 month or hospital discharge (even if weight is still less than 2,000 grams), whichever comes first. Complete the vaccine series per the recommended schedule.

For preterm infants weighing 2,000 grams or more at birth, follow the recommendations for full-term infants including a HepB dose within 24 hours of birth.

Last reviewed: July 21, 2023

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