title: Effectiveness of influenza vaccine against life-threatening RT-PCR-confirmed influenza illness in US children, 2010-2012.
abstract: BACKGROUND
  No studies have examined the effectiveness of influenza vaccine against intensive care unit (ICU) admission associated with influenza virus infection among children.
  
  
  METHODS
  In 2010-2011 and 2011-2012, children aged 6 months to 17 years admitted to 21 US pediatric intensive care units (PICUs) with acute severe respiratory illness and testing positive for influenza were enrolled as cases; children who tested negative were PICU controls. Community controls were children without an influenza-related hospitalization, matched to cases by comorbidities and geographic region. Vaccine effectiveness was estimated with logistic regression models.
  
  
  RESULTS
  We analyzed data from 44 cases, 172 PICU controls, and 93 community controls. Eighteen percent of cases, 31% of PICU controls, and 51% of community controls were fully vaccinated. Compared to unvaccinated children, children who were fully vaccinated were 74% (95% CI, 19% to 91%) or 82% (95% CI, 23% to 96%) less likely to be admitted to a PICU for influenza compared to PICU controls or community controls, respectively. Receipt of 1 dose of vaccine among children for whom 2 doses were recommended was not protective.
  
  
  CONCLUSIONS
  During the 2010-2011 and 2011-2012 US influenza seasons, influenza vaccination was associated with a three-quarters reduction in the risk of life-threatening influenza illness in children.
authors.affiliation: Influenza Division, US Centers for Disease Control and Prevention Battelle Memorial Institute, Atlanta, Georgia.
authors.forename: Jill M
authors.initials: JM
authors.lastname: Ferdinands
authors.affiliation: Abt Associates, Inc., Cambridge.
authors.forename: Lauren E W
authors.initials: LE
authors.lastname: Olsho
authors.affiliation: Department of Anesthesia, Perioperative and Pain Medicine (Critical Care), Boston Children's Hospital, Massachusetts.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Agan
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Niranjan
authors.initials: N
authors.lastname: Bhat
authors.affiliation: Department of Anesthesia, Perioperative and Pain Medicine (Critical Care), Boston Children's Hospital, Massachusetts.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Sullivan
authors.affiliation: Division of Critical Care Medicine, Nationwide Children's Hospital, Columbus, Ohio.
authors.forename: Mark
authors.initials: M
authors.lastname: Hall
authors.affiliation: Section of Critical Care Medicine, Department of Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Mourani
authors.affiliation: Influenza Division, US Centers for Disease Control and Prevention.
authors.forename: Mark
authors.initials: M
authors.lastname: Thompson
authors.affiliation: Department of Anesthesia, Perioperative and Pain Medicine (Critical Care), Boston Children's Hospital, Massachusetts.
authors.forename: Adrienne G
authors.initials: AG
authors.lastname: Randolph
mesh_terms: D000293:Adolescent; D000818:Animals; D002648:Child; D002675:Child, Preschool; D003422:Critical Care / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D009975:Orthomyxoviridae / Q000235:genetics / Q000302:isolation & purification; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology
chemical_list: D007252:Influenza Vaccines; D012367:RNA, Viral
keywords: case-control studies; child; influenza infection; influenza vaccines; intensive care; respiratory failure