title: Effectiveness of seasonal trivalent influenza vaccine for preventing influenza virus illness among pregnant women: a population-based case-control study during the 2010-2011 and 2011-2012 influenza seasons.
abstract: BACKGROUND
  Although vaccination with trivalent inactivated influenza vaccine (TIV) is recommended for all pregnant women, no vaccine effectiveness (VE) studies of TIV in pregnant women have assessed laboratory-confirmed influenza outcomes.
  
  
  METHODS
  We conducted a case-control study over 2 influenza seasons (2010-2011 and 2011-2012) among Kaiser Permanente health plan members in 2 metropolitan areas in California and Oregon. We compared the proportion vaccinated among 100 influenza cases (confirmed by reverse transcription polymerase chain reaction) with the proportions vaccinated among 192 controls with acute respiratory illness (ARI) who tested negative for influenza and 200 controls without ARI (matched by season, site, and trimester).
  
  
  RESULTS
  Among influenza cases, 42% were vaccinated during the study season compared to 58% and 63% vaccinated among influenza-negative controls and matched ARI-negative controls, respectively. The adjusted VE of the current season vaccine against influenza A and B was 44% (95% confidence interval [CI], 5%-67%) using the influenza-negative controls and 53% (95% CI, 24%-72%) using the ARI-negative controls. Receipt of the prior season's vaccine, however, had an effect similar to receipt of the current season's vaccine. As such, vaccination in either or both seasons had statistically similar adjusted VE using influenza-negative controls (VE point estimates range = 51%-76%) and ARI-negative controls (48%-76%).
  
  
  CONCLUSIONS
  Influenza vaccination reduced the risk of ARI associated with laboratory-confirmed influenza among pregnant women by about one-half, similar to VE observed among all adults during these seasons.
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Thompson
authors.forename: De-Kun
authors.initials: DK
authors.lastname: Li
authors.forename: Pat
authors.initials: P
authors.lastname: Shifflett
authors.forename: Leslie Z
authors.initials: LZ
authors.lastname: Sokolow
authors.forename: Jeannette R
authors.initials: JR
authors.lastname: Ferber
authors.forename: Samantha
authors.initials: S
authors.lastname: Kurosky
authors.forename: Sam
authors.initials: S
authors.lastname: Bozeman
authors.forename: Sue B
authors.initials: SB
authors.lastname: Reynolds
authors.forename: Roxana
authors.initials: R
authors.lastname: Odouli
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Henninger
authors.forename: Tia L
authors.initials: TL
authors.lastname: Kauffman
authors.forename: Lyndsay A
authors.initials: LA
authors.lastname: Avalos
authors.forename: Sarah
authors.initials: S
authors.lastname: Ball
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Williams
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Irving
authors.forename: David K
authors.initials: DK
authors.lastname: Shay
authors.forename: Allison L
authors.initials: AL
authors.lastname: Naleway
mesh_terms: D000328:Adult; D002140:California / Q000453:epidemiology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D009922:Oregon / Q000453:epidemiology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology* / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines
keywords: acute respiratory illness; influenza; influenza vaccines; pregnancy; vaccine effectiveness