title: Antibody response to influenza A(H1N1)pdm09 in vaccinated, serologically infected and unaffected pregnant women and their newborns.
abstract: OBJECTIVE
  To evaluate the serological response in pregnant Danish women immunized during the 2009 pandemic by serologic infection or by vaccination with influenza A(H1N1) Pandemrix(®) and describe levels of passively acquired maternal antibody in their offspring.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  Department of Obstetrics, Aarhus University Hospital, Skejby, Denmark, October to December 2009.
  
  
  METHODS
  Pregnant women and their offspring
  
  
  METHODS
  Serological analysis of antibodies to influenza A(H1N1)pdm09 by hemagglutination inhibition assay in 197 women and their offspring. Blood samples were collected consecutively at delivery from the mother and the umbilical cord. In a subgroup of 124 of the 197 women, an additional blood sample from gestational weeks 9-12 was available for analysis.
  
  
  METHODS
  Seroconversion, geometric mean titer, geometric mean-fold rise and protective antibodies.
  
  
  RESULTS
  33 of the 124 subgroup women (27%) seroconverted during pregnancy, 79% after vaccination and 17% after serologic infection (p < 0.001). The geometric mean titer after delivery in non-vaccinated, non-serologically infected women was 17.1 (95%CI 15.7-18.6). The geometric mean titer increased significantly after serologic infection with H1N1 [76.5 (95%CI 51.3-113.9), p < 0.001] and after vaccination [589.6 (95%CI 339.3-1024.7), p < 0.001]. The geometric mean-fold rise (mother at delivery/mother early pregnancy) was significantly higher after vaccination [2.23 (1.93-2.54)] than after serologic infection [1.73 (1.59-1.87), p = 0.013]. In newborns of vaccinated mothers, 89.5% had protective antibody levels compared with 15.8% in newborns of serologically infected mothers (p < 0.001).
  
  
  CONCLUSIONS
  Influenza vaccination during pregnancy confers passive immunity to the newborn.
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Rikke B
authors.initials: RB
authors.lastname: Helmig
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Rikke D
authors.initials: RD
authors.lastname: Maimburg
authors.affiliation: Department of Immunology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Erikstrup
authors.affiliation: Department of Microbiological Diagnostics and Virology, Statens Seruminstitut, Copenhagen, Denmark.
authors.forename: Henriette S
authors.initials: HS
authors.lastname: Nielsen
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Olav B
authors.initials: OB
authors.lastname: Petersen
authors.affiliation: Department of Microbiological Diagnostics and Virology, Statens Seruminstitut, Copenhagen, Denmark.|Health Sciences, Aalborg University, Aalborg, Denmark.
authors.forename: Lars P
authors.initials: LP
authors.lastname: Nielsen
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Lone
authors.initials: L
authors.lastname: Hvidman
authors.affiliation: Pediatric Department, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Jens E
authors.initials: JE
authors.lastname: Veirum
authors.affiliation: Pediatric Department, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Tine B
authors.initials: TB
authors.lastname: Henriksen
authors.affiliation: Department of Infectious Diseases, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Merete
authors.initials: M
authors.lastname: Storgaard
mesh_terms: D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D000917:Antibody Formation; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control*; D058873:Pandemics; D049590:Postpartum Period / Q000097:blood; D011247:Pregnancy
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; C556153:pandemrix
keywords: antibody; immunity; influenza A(H1N1)pdm09; newborn; pregnancy; vaccination