What is the recommended treatment for a newborn born to a mother with a positive Hepatitis B (HB) surface antigen?

Treatment of Newborn with HBsAg-Positive Mother

All infants born to HBsAg-positive mothers must receive both hepatitis B vaccine and hepatitis B immune globulin (HBIG) 0.5 mL within 12 hours of birth, administered at different injection sites such as separate limbs. 1

Immediate Birth Management (Within 12 Hours)

• Administer single-antigen hepatitis B vaccine at one injection site (e.g., right anterolateral thigh for infants <1 year) 1
• Administer HBIG 0.5 mL at a separate anatomical site (e.g., left anterolateral thigh) 1, 2
• Do not use combination vaccines (such as Pediarix) for the birth dose—only single-antigen vaccine is appropriate 1
• This dual prophylaxis regimen is 85-95% effective at preventing chronic HBV infection in exposed infants 1, 2

Completing the Vaccine Series

For Infants ≥2,000 grams at Birth:

• Administer 3 total doses of hepatitis B vaccine on a schedule of birth, 1-2 months, and 6 months 1
• The birth dose counts as the first dose in the series for these infants 1
• The final dose must not be given before 24 weeks (164 days) of age to ensure adequate immunogenicity 1

For Preterm Infants <2,000 grams at Birth:

• Administer 4 total doses because the birth dose does NOT count toward the series due to reduced immunogenicity 1, 3
• Give 3 additional doses starting at 1 month of age, then at 2-3 months, and finally at 6 months 1, 3
• The final dose must not be given before 24 weeks (164 days) of age 1, 3
• Seroconversion rates are only 77% when preterm infants <2,000g are vaccinated in the first week, compared to 98% in term infants, justifying the extra dose 3

Post-Vaccination Serologic Testing (Critical for All Exposed Infants)

• Test for both anti-HBs and HBsAg at 9-12 months of age (generally at the next well-child visit after completing the vaccine series) 1
• Do not test before 9 months to avoid detecting passive anti-HBs from the HBIG given at birth and to maximize detection of late HBV infection 1
• Use an anti-HBs assay that detects the protective concentration of ≥10 mIU/mL 1
• Do not test for anti-HBc because passively acquired maternal anti-HBc may be detected up to 24 months of age 1

Interpretation and Management of Test Results:

If HBsAg-negative and anti-HBs ≥10 mIU/mL:

• The infant is protected and needs no further medical management 1

If HBsAg-negative but anti-HBs <10 mIU/mL:

• Administer a single booster dose of hepatitis B vaccine and retest 1-2 months later 1
• If anti-HBs remains <10 mIU/mL after the single booster, complete a second full series with two additional doses, then retest 1-2 months after the final dose 1
• Alternatively, based on clinical circumstances or family preference, you may give a complete second 3-dose series followed by testing 1-2 months after the final dose 1
• Do not administer additional doses beyond two complete vaccine series, as available data show no benefit 1

If HBsAg-positive:

• The infant has chronic HBV infection and should be referred for appropriate hepatitis specialist follow-up 1

Special Circumstances and Common Pitfalls

Breastfeeding:

• Infants may be breastfed immediately after birth once they have received both vaccine and HBIG 1
• Avoiding breastfeeding has no impact on preventing mother-to-child transmission when proper immunoprophylaxis is given 4

Interfacility Transfer:

• Staff at both transferring and receiving facilities must communicate regarding the infant's hepatitis B vaccination and HBIG receipt status to ensure timely prophylaxis 1
• This prevents the critical error of assuming prophylaxis was given at the birth hospital when it was not 1

Maternal High Viral Load:

• Transmission still occurs in 8-30% of mothers with HBV DNA >200,000 IU/mL (approximately 10^6 copies/mL) despite standard immunoprophylaxis 4, 5
• All four infected infants in one study were born to mothers with viral loads in the ninth or tenth decile 5
• Maternal antiviral therapy during late pregnancy is the most effective method to reduce transmission from mothers with high viremia, though this is a prenatal intervention 4

Combination Vaccines:

• Pediarix may be used at ≥6 weeks of age to complete the vaccine series after the birth dose of single-antigen vaccine and HBIG, though this is not in the manufacturer's labeling 1
• Never use combination vaccines for the birth dose 1

Maternal Risk Factors Associated with Transmission Failure:

• Younger maternal age, Asian/Pacific Islander race, and maternal HBeAg positivity are associated with higher transmission rates 5
• Infants receiving <3 vaccine doses have significantly higher infection rates 5

Documentation Requirements:

• Maternal HBsAg status must be clearly documented with a copy of the original laboratory report in the infant's medical record 3
• This prevents confusion and ensures appropriate prophylaxis is given 3