title: Live attenuated seasonal and pandemic influenza vaccine in school-age children: a randomized controlled trial.
abstract: BACKGROUND
  The novel influenza A(H1N1pdm09) virus emerged in North America in early 2009 and rapidly spread worldwide. In this study we report the efficacy of the live attenuated monovalent H1N1pdm09 vaccine and 2009-10 seasonal influenza vaccine in a randomized double-blind placebo-controlled trial.
  
  
  METHODS
  We enrolled 703 children aged 7-11. Each child was randomly allocated in the ratio 3:2 to receive one dose of live attenuated monovalent H1N1pdm09 vaccine or saline placebo between November 2009 and January 2010, followed after 3-10 weeks by independent random allocation to one dose of live attenuated trivalent 2009-10 seasonal influenza vaccine or saline placebo in the same ratio. Children were followed up through September 2010 with biweekly telephone calls and symptom diaries. Seasonal and pandemic influenza infections were confirmed by virologic testing of nose and throat swabs collected during acute respiratory illnesses.
  
  
  RESULTS
  Overall, 30 children had confirmed influenza including 3 (0.43%) H1N1pdm09, 10 (1.4%) seasonal A(H3N2), and 17 (2.4%) influenza B. There were no significant differences in incidence rates of H1N1pdm09 or A(H3N2) between the four study arms, but receipt of the seasonal influenza vaccine was associated with a significant reduction in risk of influenza B (p<0.01). Vaccine efficacy against confirmed H1N1pdm09 infection associated with receipt of the monovalent H1N1pdm09 vaccine was 65% (95% confidence interval, CI: -281%, 97%). Vaccine efficacies against confirmed seasonal influenza A(H3N2) and B infection associated with receipt of the seasonal influenza vaccine were 31% (95% CI: -138%, 80%) and 96% (95% CI: 67%, 99%) respectively.
  
  
  CONCLUSIONS
  Vaccine efficacy was consistent with other studies of the monovalent H1N1pdm09 vaccine and seasonal influenza vaccines. Our study was underpowered to provide precise estimates of vaccine efficacy due to low incidence of influenza A viruses during the study period.
authors: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong Special Administrative Region.
authors: Brendan
authors: B
authors: Klick
authors: Sunita
authors: S
authors: Durrani
authors: Kwok-Hung
authors: KH
authors: Chan
authors: Dennis K M
authors: DK
authors: Ip
authors: Erica S K
authors: ES
authors: Chou
authors: Henry K H
authors: HK
authors: Kwok
authors: Sophia
authors: S
authors: Ng
authors: Susan S
authors: SS
authors: Chiu
authors: J S Malik
authors: JS
authors: Peiris
authors: Gabriel M
authors: GM
authors: Leung
authors: Benjamin J
authors: BJ
authors: Cowling
mesh_terms: D002648:Child; D016001:Confidence Intervals; D004311:Double-Blind Method; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology / Q000302:isolation & purification; D009981:Influenza B virus / Q000276:immunology / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D008297:Male; D009656:North America; D058873:Pandemics / Q000517:prevention & control / Q000706:statistics & numerical data; D010919:Placebos; D012306:Risk; D012621:Seasons; D013045:Species Specificity; D014613:Vaccines, Attenuated / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: D007252:Influenza Vaccines; D010919:Placebos; D014613:Vaccines, Attenuated