EFFECT OF NEONATAL IMMUNIZATION WITH DIPHTHERIA AND TETANUS TOXOIDS ON ANTIBODY-RESPONSES TO HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINES

We randomly assigned 150 newborn infants to receive diphtheria and tet anus toxoids (DT) or Hib oligosaccharide conjugate (HbOC) at birth to determine whether exposure to the Hoemophilus influenzae type b (Hib) conjugate vaccines' carrier proteins would enhance immune responses to subsequent administrations of HbOC;or PbP-tetanus toroid conjugate (P RP-T) at 2, 4, and 6 months of age, Their antibody responses were comp ared with those of 100 children immunized with HbOC or PRP-T beginning at 2 months of age, No serious adverse reactions were associated with neonatal vaccination. Administration of HbOd at birth]did not lead to earlier or higher antibody levels, Newborn immunization with DT did n ot prime children for enhanced antibody responses, Moreover, Hib antib ody levels were lower in DT-primed children than in children immunized beginning at 2 months of age, Diphtheria antibody levels, but not tet anus antibody levels, were also lower in children immunized with DT at birth. We conclude that neonatal immunization with Hib conjugate vacc ines is not a means to provide earlier protection against invasive Hib disease, Newborn DT administration does not enhance subsequent antibo dy responses to Hib conjugate vaccines, and may lead to suppression of Hib and diphtheria antibody responses.