title: Neonatal immunization: response to Haemophilus influenzae type b-tetanus toxoid conjugate vaccine.
abstract: OBJECTIVE
  To study the immunogenicity and tolerability of Haemophilus influenzae type b (Hib) conjugate vaccine administered in the neonatal period.
  
  
  METHODS
  Hib capsular polysaccharide (PS)-tetanus toxoid conjugate vaccine (PRP-T) was given to 120 neonates at 2 days of age, followed by PRP-T or the Hib PS vaccine at 4 months and a PRP-T booster at 14 months. Their anti-Hib PS concentrations were compared with those in children receiving PRP-T at 2 and 4 months or at 4 months.
  
  
  RESULTS
  No serious adverse reactions were noted. The geometric mean concentration of anti-Hib PS at the age of 2 days was 0.34 micrograms/mL and at 4 months was 0.12 micrograms/mL. This was significantly more than the concentration in unimmunized infants at this age and 3.5 times more than expected, taking into account the natural decay of transplacentally acquired antibodies. Such a response was not seen in infants with a high (greater than 3.0 micrograms/mL) neonatal antibody concentration. The PRP-T vaccine given at 4 months elicited an antibody response in all infants and Hib PS in 62%, indicating immunologic priming. At 14 months, a higher percentage of the infants who had received PRP-T at 2 days and 4 months than of those who had received PRP-T at 4 months only had anti-Hib PS concentrations greater than 0.15 micrograms/mL. All infants responded well to the booster at 14 months. There was no evidence of immunologic tolerance.
  
  
  CONCLUSIONS
  Neonatal immunization with PRP-T was safe and well tolerated in Finnish infants, and it would be worthwhile to further study its effects in higher risk populations.
authors.affiliation: National Public Health Institute, Helsinki, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Kurikka
authors.forename: H
authors.initials: H
authors.lastname: Käyhty
authors.forename: H
authors.initials: H
authors.lastname: Peltola
authors.forename: L
authors.initials: L
authors.lastname: Saarinen
authors.forename: J
authors.initials: J
authors.lastname: Eskola
authors.forename: P H
authors.initials: PH
authors.lastname: Mäkelä
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D016667:Bacterial Capsules / Q000276:immunology; D005500:Follow-Up Studies; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology*; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D007115:Immunization Schedule; D007117:Immunization, Secondary; D007223:Infant; D007231:Infant, Newborn / Q000276:immunology*; D013745:Tetanus Toxoid / Q000008:administration & dosage / Q000276:immunology*; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; D013745:Tetanus Toxoid; D018074:Vaccines, Conjugate