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 antibo dy in maternal and cord blood following maternal vaccination in pregnancy a nd to determine the level of maternal hepatitis B surface antibody (HbsAb) associated with a seroprotective level in cord blood. Thirty-seven (37) hea lthy gravidas who were identified as seronegative for hepatitis B surface a ntigen (HbsAg) and antibody (HbsAb) on initial prenatal assessment and subs equently began a series of three vaccinations in the pregnancy with hepatit is 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 hep atitis B vaccination to all patients testing seronegative to HbsAg and HbsA b. All gravidas were given a dose of 20 mu g into the deltoid muscle utiliz ing 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 enz yme-linked immunoadsorbent assay (ELISA) analysis (AUSAB-EIA Abbott Lab; Ab bott Park, IL). A serum titer of greater than or equal to 10 mLU/mL was con sidered seroprotective. Maternal and cord blood groups identified by seropr otection 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 o f delivery. Of these, 16 (88%) had seroprotective cord blood levels. All ma ternal 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 diffe rence in the frequency of cord blood seroprotection comparing groups by num ber of maternal vaccine doses received. When maternal liters of HbsAb achie ve seroprotective levels following vaccination, cord blood seroprotection w as 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.