title: Immunogenicity of an inactivated hepatitis A vaccine in infants and young children.
abstract: BACKGROUND
  Infants with passively transferred maternal antibody, born to mothers immune to hepatitis A virus (HAV), have a blunted response to hepatitis A (HA) vaccine. We compared HA vaccine immunogenicity among infants born to immune and susceptible mothers, vaccinated on different schedules.
  
  
  METHODS
  Infants were randomized into 3 groups, each receiving 2 doses of 720 EL.U. of HA vaccine (HAVRIX; Glaxo SmithKline): group 1 at ages 6 and 12 months, group 2 at ages 12 and 18 months and group 3 at ages 15 and 21 months. We determined mothers' antibody to HAV (anti-HAV) status and infants' anti-HAV concentrations at the first vaccine dose (baseline) and at 1, 7 and 12 months thereafter. All were tested at age 13 months for responses to recommended routine vaccinations administered during infancy.
  
  
  RESULTS
  Of 248 participants, 140 were born to HA-susceptible mothers and 108 to immune mothers. At baseline, 34 of 36 (94%) group 1, 5 of 34 (15%) group 2 and one of 38 (3%) group 3 infants born to immune mothers were seropositive. By month 7, all participants in all groups were seropositive except group 1 infants born to immune mothers (34 of 36 [94%], seropositive). In group 1, peak geometric mean concentrations between infants born to immune (794 mIU/mL) and susceptible (2083 mIU/mL) mothers were significantly different. Across groups, peak geometric mean concentrations were similar among infants born to susceptible mothers (3166 mIU/mL, group 2; 3153 mIU/mL, group 3). Among infants born to immune mothers, the difference between groups 1 and 3 (2715 mIU/mL) was significant. There were no differences in responses to routine vaccinations.
  
  
  CONCLUSIONS
  HA vaccine is immunogenic among infants born to HA-susceptible mothers and those born to immune mothers and vaccinated beginning > or =12 months old. Passively transferred maternal antibody persists for at least 6 months and results in a blunted response to HA vaccination.
authors.affiliation: Division of Viral Hepatitis, Centers for Disease Control and Prevention, Atlanta, GA, USA. bzb8@cdc.gov
authors.forename: Beth P
authors.initials: BP
authors.lastname: Bell
authors.forename: Susan
authors.initials: S
authors.lastname: Negus
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Fiore
authors.forename: Julia
authors.initials: J
authors.lastname: Plotnik
authors.forename: Kathy Boaz
authors.initials: KB
authors.lastname: Dhotre
authors.forename: James
authors.initials: J
authors.lastname: Williams
authors.forename: Craig N
authors.initials: CN
authors.lastname: Shapiro
authors.forename: Brian J
authors.initials: BJ
authors.lastname: McMahon
mesh_terms: D000367:Age Factors; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D035922:Hepatitis A Antibodies / Q000097:blood*; D022362:Hepatitis A Vaccines / Q000008:administration & dosage / Q000276:immunology*; D030041:Hepatitis A virus / Q000276:immunology; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007115:Immunization Schedule; D007223:Infant
chemical_list: D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines