Correlation of maternal and fetal hepatitis B antibody titers following maternal vaccination in pregnancy

The objective of this study was to compare the levels of hepatitis B antibody in maternal and cord blood following maternal vaccination in pregnancy and to determine the level of maternal hepatitis B surface antibody (HbsAb) associated with a seroprotective level in cord blood. Thirty-seven (37) healthy gravidas who were identified as seronegative for hepatitis B surface antigen (HbsAg) and antibody (HbsAb) on initial prenatal assessment and subsequently began a series of three vaccinations in the pregnancy with hepatitis B recombinant DNA vaccine (Engerix-B, SmithKline Beecham) were studied. These mothers represented the first group of gravidas delivering between 6/1/97 and 8/1/97 following the iniatiation of a new protocol of offering hepatitis B vaccination to all patients testing seronegative to HbsAg and HbsAb. All gravidas were given a dose of 20 mu g into the deltoid muscle utilizing a 1 1/2-inch needle at a schedule of 0, 1, and 6 months. At the time of delivery specimens were obtained for maternal serum levels and paired cord blood levels of HbsAb. Levels were determined utilizing a quantitative enzyme-linked immunoadsorbent assay (ELISA) analysis (AUSAB-EIA Abbott Lab; Abbott Park, IL). A serum titer of greater than or equal to 10 mLU/mL was considered seroprotective. Maternal and cord blood groups identified by seroprotection status were then sudivided by number of maternal vaccines received. Data were compared using the Student's t-test and Chi-square or Fisher's exact test. Eighteen gravidas (49%) had seroprotective titers at the lime of delivery. Of these, 16 (88%) had seroprotective cord blood levels. All maternal specimens with a HbsAb titer greater than or equal to 35 mLU/mL were associated with cord blood tiers greater than or equal to 10 mLU/mL. When maternal titers achieved seroprotective levels of HbsAb, there was no difference in the frequency of cord blood seroprotection comparing groups by number of maternal vaccine doses received. When maternal liters of HbsAb achieve seroprotective levels following vaccination, cord blood seroprotection was achieved in 88% of studied patients. Maternal HbsAb liters greater than or equal to 35 mLU/mL were associated with cord blood seroprotective levels in all cases.