title: Immune response to Haemophilus influenzae type b conjugate vaccine in preterm infants.
abstract: BACKGROUND
  Haemophilus influenzae type b (Hib) vaccine became available for use in Japan in December 2008. The aim of the present study was to evaluate the immunogenicity of Hib vaccine in Japanese preterm infants.
  
  
  METHODS
  Serum samples were obtained from 54 preterm infants before the first vaccination and 1 month after the third. Anti-polyribosylribitol phosphate (PRP) antibodies were measured using an enzyme-linked immunosorbent assay method. Antibody positivity was defined as levels >1 µg/mL.
  
  
  RESULTS
  Of the 54 preterm infants, 46 (85.2%) achieved antibody levels >1 µg/mL. This compares with the 92.4% reported in full-term infants. The antibody seroconversion rate of infants starting vaccination at 2 months of age was close to being significantly lower than when vaccination was started at 3 months of age (P= 0.060). In addition, the percentage of infants achieving a positive response in the group with a history of antenatal steroid exposure was significantly higher than in those not exposed (P= 0.046). Thus, risk factors for lower Hib antibody concentrations after three doses of vaccine were age at first vaccination and lack of use of antenatal steroids.
  
  
  CONCLUSIONS
  There is a possibility that perinatal factors and the environment unique to preterm infants are related to their lower antibody positivity rates compared to full-term infants. It may therefore be preferable to modify the proposed immunization schedule.
authors: Perinatal Center for Maternity and Neonate Department of Pediatrics, Yokohama City University Medical Center, Yokohama, Kanagawa 232-0024, Japan. tsudaken@bk2.so-net.ne.jp
authors: Kennosuke
authors: K
authors: Tsuda
authors: Shiho
authors: S
authors: Iwasaki
authors: Haruko
authors: H
authors: Horiguchi
authors: Masaaki
authors: M
authors: Mori
authors: Shigeru
authors: S
authors: Nishimaki
authors: Kazuo
authors: K
authors: Seki
authors: Masataka
authors: M
authors: Taguri
authors: Shumpei
authors: S
authors: Yokota
authors: Naruhiko
authors: N
authors: Ishiwada
mesh_terms: D016667:Bacterial Capsules / Q000276:immunology*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006192:Haemophilus Infections / Q000276:immunology / Q000517:prevention & control*; D018073:Haemophilus Vaccines / Q000276:immunology*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000276:immunology*; D007235:Infant, Premature, Diseases / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D011247:Pregnancy; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D018074:Vaccines, Conjugate