title: The burden of influenza hospitalizations in infants from 2003 to 2012, United States.
abstract: BACKGROUND
  Little information is available describing the epidemiology and clinical characteristics of those <12 months hospitalized with influenza, particularly at a population level.
  
  
  METHODS
  We used population-based, laboratory-confirmed influenza hospitalization surveillance data from 2003 to 2012 seasons to describe the impact of influenza by age category (<3, 3 to <6 and 6 to <12 months). Logistic regression was used to explore risk factors for intensive care unit (ICU) admission. Adjusted age-specific, influenza-associated hospitalization rates were calculated and applied to the number of US infants to estimate national numbers of hospitalizations.
  
  
  RESULTS
  Influenza was associated with an annual average of 6514 infant hospitalizations (range 1842-12,502). Hospitalization rates among infants <3 months were substantially higher than the rate in older infants. Most hospitalizations occurred in otherwise healthy infants (75%) among whom up to 10% were admitted to the ICU and up to 4% had respiratory failure. These proportions were 2-3 times higher in infants with high risk conditions. Infants <6 months were 40% more likely to be admitted to the ICU than older infants. Lung disease (adjusted odds ratio 1.80; 95% confidence interval 1.22-2.67), cardiovascular disease (adjusted odds ratio: 4.16; 95% confidence interval: 2.65-6.53), and neuromuscular disorder (adjusted odds ratio: 2.99; 95% confidence interval: 1.87-4.78) were risk factors for ICU admission among all infants.
  
  
  CONCLUSIONS
  The impact of influenza on infants, particularly those very young or with high risk conditions, underscores the importance of influenza vaccination, especially among pregnant women and those in contact with young infants not eligible for vaccination.
authors.affiliation: From the *Centers for Disease Control and Prevention; †Emory University School of Medicine; ‡Atlanta Veterans Administration Medical Center, Atlanta, GA; §Colorado Department of Public Health and Environment, Denver, CO; ¶Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN; ‖Michigan Department of Community Health, Lansing, MI; **Connecticut Emerging Infections Program, School of Public Health, New Haven, CT; ††Oregon Public Health Division, Portland, OR; ‡‡Utah Department of Health, Salt Lake City, UT; §§New Mexico Department of Health, Santa Fe, NM; ¶¶Rhode Island Department of Health, Providence, RI; ‖‖Minnesota Department of Health, St. Paul, MN; ***Emerging Infections Program, New York State Department of Health, Albany, NY; †††California Emerging Infections Program, Oakland, CA; ‡‡‡Department of Medicine, University of Rochester School of Medicine and Dentistry; §§§Monroe County, Department of Public Health, Rochester, NY; ¶¶¶Maryland Department of Health and Mental Hygiene, Baltimore, MD; and ‖‖‖Ohio Department of Health, Columbus, OH.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Chaves
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perez
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
authors.forename: Lisa
authors.initials: L
authors.lastname: Miller
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: Mary L
authors.initials: ML
authors.lastname: Lindegren
authors.forename: Ruta
authors.initials: R
authors.lastname: Sharangpani
authors.forename: James
authors.initials: J
authors.lastname: Meek
authors.forename: Kimberley
authors.initials: K
authors.lastname: Yousey-Hindes
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: Rachelle
authors.initials: R
authors.lastname: Boulton
authors.forename: Joan
authors.initials: J
authors.lastname: Baumbach
authors.forename: Emily B
authors.initials: EB
authors.lastname: Hancock
authors.forename: Ananda S
authors.initials: AS
authors.lastname: Bandyopadhyay
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
authors.forename: Craig
authors.initials: C
authors.lastname: Morin
authors.forename: Shelley M
authors.initials: SM
authors.lastname: Zansky
authors.forename: Arthur
authors.initials: A
authors.lastname: Reingold
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Bennett
authors.forename: Patricia
authors.initials: P
authors.lastname: Ryan
authors.forename: Brian
authors.initials: B
authors.lastname: Fowler
authors.forename: Alicia
authors.initials: A
authors.lastname: Fry
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000367:Age Factors; D002318:Cardiovascular Diseases / Q000453:epidemiology; D003422:Critical Care / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007251:Influenza, Human / Q000150:complications / Q000453:epidemiology*; D008171:Lung Diseases / Q000453:epidemiology; D008297:Male; D009468:Neuromuscular Diseases / Q000453:epidemiology; D012131:Respiratory Insufficiency / Q000453:epidemiology / Q000821:virology; D012307:Risk Factors; D014481:United States / Q000453:epidemiology