title: Influenza in Infants Born to Women Vaccinated During Pregnancy.
abstract: Infants <6 months old with influenza are at risk for adverse outcomes. Our objective was to compare influenza outcomes in infants <6 months old born to women who did and did not report influenza vaccine during pregnancy.
  
  
  
  The study included all women who delivered from 12/2005 to 3/2014 at Intermountain facilities and their infants. Influenza outcomes included infant influenza-like illness (ILI), laboratory-confirmed influenza, and influenza hospitalizations.
  
  
  
  The cohort included 245 386 women and 249 387 infants. Overall, 23 383 (10%) pregnant women reported influenza immunization. This number increased from 2.2% before the H1N1 pandemic to 21% postpandemic (P < .001). A total of 866 infants <6 months old had ≥1 ILI encounter: 32 (1.34/1000) infants born to women reporting immunization and 834 (3.70/1000) born to women who did not report immunization (relative risk [RR] 0.36; 95% confidence interval [CI], 0.26-0.52; P < .001). A total of 658 infants had laboratory-confirmed influenza: 20 (0.84/1000) born to women reporting immunization and 638 (2.83/1000) born to unimmunized women (RR 0.30; 95% CI, 0.19-0.46; P < .001). A total of 151 infants with laboratory-confirmed influenza were hospitalized: 3 (0.13/1000) born to women reporting immunization and 148 (0.66/1000) born to unimmunized women (RR 0.19; 95% CI, 0.06-0.60; P = .005).
  
  
  
  Self-reported influenza immunization during pregnancy was low but increased after the H1N1 pandemic. Infants born to women reporting influenza immunization during pregnancy had risk reductions of 64% for ILI, 70% for laboratory-confirmed influenza, and 81% for influenza hospitalizations in their first 6 months. Maternal influenza immunization during pregnancy is a public health priority.
authors.affiliation: Departments of Pediatrics, and julie.shakib@hsc.utah.edu.
authors.forename: Julie H
authors.initials: JH
authors.lastname: Shakib
authors.affiliation: Intermountain Healthcare, Salt Lake City, Utah.
authors.forename: Kent
authors.initials: K
authors.lastname: Korgenski
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Angela P
authors.initials: AP
authors.lastname: Presson
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Sheng
authors.affiliation: Obstetrics and Gynecology, University of Utah, Salt Lake City, Utah; and.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Varner
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Pavia
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Byington
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007061:Idaho / Q000453:epidemiology; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D058873:Pandemics; D011247:Pregnancy; D012306:Risk; D057566:Self Report; D014589:Utah / Q000453:epidemiology
chemical_list: D007252:Influenza Vaccines