TRANSPLACENTAL ANTIBODY TRANSFER FOLLOWING MATERNAL IMMUNIZATION WITHPOLYSACCHARIDE AND CONJUGATE HAEMOPHILUS-INFLUENZAE TYPE-B VACCINES

Passive transfer of antibody to infants born to women immunized during the third trimester of pregnancy with a Haemophilus influenzae type b (Hib) vaccine (PRP polysaccharide or Hib conjugates PRP-D or HbOC) wa s studied in 50 mothers and infants and 47 nonimmunized mother-infant pairs. Geometric mean total PRP antibody by RIA was 1.2 mu g/mL at del ivery in unimmunized women and 21, 149, and 171 mu g/mL in women who r eceived PRP, PRP-D, and HbOC, respectively. Mean cord PRP antibody lev els were 0.29, 3.0, 17.5, and 29.3 mu g/mL for the corresponding group s. Postimmunization and cord PRP antibody levels were higher after mat ernal immunization with conjugate vaccines than with PRP vaccine (P <. 01). PRP Ige1 subclass was transmitted more efficiently than IgG2 (56% vs, 35%, P <.01). The proportion of anti-PRP IgG transmitted from imm unized mothers to infants correlated with time between immunization an d delivery. Administration of PRP conjugate vaccines to women during p regnancy resulted in higher levels of PRP antibodies in infants than d id polysaccharide or no vaccine.