Update: Shortened Interval for Postvaccination Serologic Testing of Infants Born to Hepatitis B-Infected Mothers.

Infants born to hepatitis B-infected mothers receive postexposure prophylaxis to reduce their risk for perinatal hepatitis B virus (HBV) infection. Postexposure prophylaxis consists of hepatitis B (HepB) vaccine and hepatitis B immune globulin administered within 12 hours of birth, followed by completion of the 3-dose or 4-dose HepB vaccine series. Postvaccination serologic testing (PVST) assesses an infant's response to HepB vaccination and has typically occurred at age 9-18 months. This report provides a CDC update recommending shortening the interval for PVST from age 9-18 months to age 9-12 months. Providers should order PVST (consisting of hepatitis B surface antigen [HBsAg] and antibody to HBsAg [anti-HBs]) for infants born to HBsAg-positive mothers at age 9-12 months (or 1-2 months after the final dose of the vaccine series, if the series is delayed). This recommendation was prompted by the discontinuation of production of Hib/HepB vaccine (Comvax) and new data from the Enhanced Perinatal Hepatitis B Prevention Program supporting PVST 1・2 months after receipt of the last HepB vaccine dose, and at age ≥9 months.