title: Clinical and immune responses to inactivated influenza A(H1N1)pdm09 vaccine in children.
abstract: BACKGROUND
  As the influenza A H1N1 pandemic emerged in 2009, children were found to experience high morbidity and mortality and were prioritized for vaccination. This multicenter, randomized, double-blind, age-stratified trial assessed the safety and immunogenicity of inactivated influenza A(H1N1)pdm09 vaccine in healthy children aged 6 months to 17 years.
  
  
  METHODS
  Children received 2 doses of approximately 15 or 30 µg hemagglutin antigen 21 days apart. Reactogenicity was assessed for 8 days after each dose, adverse events through day 42, and serious adverse events or new-onset chronic illnesses through day 201. Serum hemagglutination inhibition titers were measured on days 0 (prevaccination), 8, 21, 29 and 42.
  
  
  RESULTS
  A total of 583 children received the first dose and 571 received the second dose of vaccine. Vaccinations were generally well-tolerated and no related serious adverse events were observed. The 15 µg dosage elicited a seroprotective hemagglutination inhibition (≥ 1:40) in 20%, 47% and 93% of children in the 6-35 month, 3-9 year and 10-17 year age strata 21 days after dose 1 and in 78%, 82% and 98% of children 21 days after dose 2, respectively. The 30 µg vaccine dosage induced similar responses.
  
  
  CONCLUSIONS
  The inactivated influenza A(H1N1)pdm09 vaccine exhibited a favorable safety profile at both dosage levels. While a single 15 or 30 µg dose induced seroprotective antibody responses in most children 10-17 years of age, younger children required 2 doses, even when receiving dosages 4- to 6-fold higher than recommended. Well-tolerated vaccines are needed that induce immunity after a single dose for use in young children during influenza pandemics.
authors.affiliation: From the *Division of Infectious Disease and Tropical Pediatrics, Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD; †Department of Pediatrics, Vanderbilt Vaccine Research Program, Vanderbilt University School of Medicine, Nashville, TN; ‡Department of Pediatrics, Pediatric Infectious Diseases Section, Children's Mercy Hospital and Clinics, and the University of Missouri-Kansas City, Kansas City, MO; §Division of Pediatric Infectious Diseases, Department of Pediatrics, University of Washington and Seattle Children's Hospital, Seattle, WA; ¶Department of Pediatrics, Duke Clinical Vaccine Unit, Duke University School of Medicine, Durham, NC; ‖Division of General Pediatrics, Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD; **Department of Medicine, Duke University School of Medicine, Durham, NC; ††Southern Research Institute, Birmingham, AL; and ‡‡EMMES Corp, Department of Vaccines and Infectious Diseases, Rockville, MD.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Kotloff
authors.forename: Natasha B
authors.initials: NB
authors.lastname: Halasa
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Harrison
authors.forename: Janet A
authors.initials: JA
authors.lastname: Englund
authors.forename: Emmanuel B
authors.initials: EB
authors.lastname: Walter
authors.forename: James C
authors.initials: JC
authors.lastname: King
authors.forename: C Buddy
authors.initials: CB
authors.lastname: Creech
authors.forename: Sara A
authors.initials: SA
authors.lastname: Healy
authors.forename: Rowena J
authors.initials: RJ
authors.lastname: Dolor
authors.forename: Ina
authors.initials: I
authors.lastname: Stephens
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.forename: Diana L
authors.initials: DL
authors.lastname: Noah
authors.forename: Heather
authors.initials: H
authors.lastname: Hill
authors.forename: Mark
authors.initials: M
authors.lastname: Wolff
mesh_terms: D000293:Adolescent; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004311:Double-Blind Method; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects* / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D015164:Vaccines, Inactivated / Q000009:adverse effects / Q000276:immunology
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated