title: Immunogenicity of an inactivated monovalent 2009 H1N1 influenza vaccine in pregnant women.
abstract: BACKGROUND
  Although pregnant women are at increased risk of severe illness following influenza infection, there is relatively little information on the immunogenicity of influenza vaccines administered during pregnancy.
  
  
  METHODS
  We conducted a clinical trial that enrolled 120 pregnant women in which participants were randomly assigned to receive an inactivated 2009 H1N1 influenza vaccine containing either 25 μg or 49 μg of hemagglutinin (HA) in a 2-dose series with a 21-day period between administration of the first and second doses.
  
  
  RESULTS
  Following the first vaccination, HA inhibition (HAI) titers of ≥1:40 were detected in 93% (95% confidence interval [CI], 82%-98%) of subjects who received the 25-μg dose and 97% (95% CI, 88%-100%) of subjects receiving the 49-μg dose. In cord blood samples, HAI titers of ≥1:40 were found in 87% (95% CI, 73%-96%) of samples from the 25-μg dose group and in 89% (95% CI, 76%-96%) from the 49-μg dose group. Microneutralization titers tended to be higher than HAI titers, but the patterns of response were similar.
  
  
  CONCLUSIONS
  In pregnant women, 1 dose of an inactivated 2009 H1N1 influenza vaccine containing 25 μg of HA elicited an antibody response typically associated with protection against influenza infection. Efficient transplacental transfer of antibody was also documented.
authors.affiliation: The Group Health Research Institute, Group Health, Seattle, Washington, USA. jackson.l@ghc.org
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Jackson
authors.forename: Shital M
authors.initials: SM
authors.lastname: Patel
authors.forename: Geeta K
authors.initials: GK
authors.lastname: Swamy
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Frey
authors.forename: C Buddy
authors.initials: CB
authors.lastname: Creech
authors.forename: Flor M
authors.initials: FM
authors.lastname: Munoz
authors.forename: Raul
authors.initials: R
authors.lastname: Artal
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Keitel
authors.forename: Diana L
authors.initials: DL
authors.lastname: Noah
authors.forename: Carey Rodeheffer
authors.initials: CR
authors.lastname: Petrie
authors.forename: Mark
authors.initials: M
authors.lastname: Wolff
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D011247:Pregnancy; D014611:Vaccination / Q000379:methods; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated