title: Effectiveness of pandemic H1N1 vaccine against influenza-related hospitalization in children.
abstract: OBJECTIVE
  Young children are generally considered immunologically naive with respect to influenza exposure opportunities; thus, a 2-dose schedule is recommended when a child is first immunized with conventional influenza vaccine lacking adjuvant. We estimated the effectiveness of a single pediatric dose of AS03-adjuvanted vaccine against hospitalization for confirmed pandemic influenza A/H1N1 (pH1N1) infection in children aged 6 months to 9 years during the fall 2009 vaccination campaign.
  
  
  METHODS
  In a matched case-control design, case subjects were children hospitalized for pH1N1 infection in the Fall of 2009, in Quebec, Canada. Controls were nonhospitalized children, matched by age and region of residence. Vaccination status in case subjects and controls was ascertained in relation to the case subject's date of illness onset. Vaccine effectiveness was estimated through conditional logistic regression.
  
  
  RESULTS
  The overall effectiveness of a single pediatric dose of vaccine administered ≥14 days before illness onset was 85% (95% confidence interval [CI]: 61% to 94%), varying according to age category but with wide and overlapping CIs: 92% (95% CI: 51% to 99%) in 6-23 month-old children, 89% (95% CI: 34% to 98%) in 2-4 year-olds, and 79% (95% CI: -31% to 96%) in 5-9 year-olds. Overall vaccine effectiveness for immunization ≥10 days before illness onset was slightly lower at 80% (95% CI: 60% to 90%), with similar variation according to age.
  
  
  CONCLUSIONS
  In children aged 6 months to 9 years, a single pediatric dose of the AS03-adjuvanted pH1N1 vaccine was highly protective against hospitalization beginning at 10 and 14 days after vaccination.
authors: Institut National de Santé Publique du Québec, Quebec City, Quebec, Canada. rodica.gilca@ssss.gouv.qc.ca
authors: Rodica
authors: R
authors: Gilca
authors: Geneviève
authors: G
authors: Deceuninck
authors: Gaston
authors: G
authors: De Serres
authors: Nicole
authors: N
authors: Boulianne
authors: Chantal
authors: C
authors: Sauvageau
authors: Caroline
authors: C
authors: Quach
authors: François D
authors: FD
authors: Boucher
authors: Danuta M
authors: DM
authors: Skowronski
mesh_terms: D017677:Age Distribution; D000704:Analysis of Variance; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D058873:Pandemics / Q000517:prevention & control* / Q000706:statistics & numerical data; D011792:Quebec / Q000453:epidemiology; D012016:Reference Values; D012189:Retrospective Studies; D017678:Sex Distribution; D014611:Vaccination / Q000379:methods*
chemical_list: D007252:Influenza Vaccines