title: Efficacy of live attenuated influenza vaccine in children 6 months to 17 years of age.
abstract: BACKGROUND
  It has been suggested that live attenuated influenza vaccine (LAIV) may be less effective in older individuals because of prior wild-type influenza infections. LAIV is currently approved in the United States, South Korea and Hong Kong for individuals 2-49 years of age.
  
  
  OBJECTIVE
  To examine data from previously published pediatric studies to determine the efficacy of LAIV in various age groups.
  
  
  METHODS
  Four studies in which the subject age range exceeded 36 months were identified: one 2-year study comparing LAIV with placebo and three 1-year studies comparing LAIV with trivalent inactivated influenza vaccine (TIV). Efficacy against any strain regardless of antigenic similarity to vaccine was analyzed by age; age groups were based on the study design and sample size. A logistic regression model was used to assess whether age, as a continuous variable, was an effect modifier on LAIV efficacy.
  
  
  RESULTS
  The efficacy of LAIV did not vary with age in children aged 15-84 months compared with placebo or in children aged 6 months to 17 years compared with TIV.
  
  
  CONCLUSIONS
  The available data from prospective, randomized studies in children does not support the concept that prior repeated exposure to influenza, either through wild-type infection or vaccination with live, attenuated or inactivated vaccines, reduces the efficacy of LAIV compared with placebo or TIV. The decreased immunologic responses to LAIV reported in older individuals or those with pre-existing immunity do not appear to translate into reduced protection from influenza in children.
authors.affiliation: Saint Louis University Health Science Center, St Louis, MO, USA. belsherb@slu.edu
authors.forename: Robert B
authors.initials: RB
authors.lastname: Belshe
authors.forename: Seth L
authors.initials: SL
authors.lastname: Toback
authors.forename: Tingting
authors.initials: T
authors.lastname: Yi
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Ambrose
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D016032:Randomized Controlled Trials as Topic; D014613:Vaccines, Attenuated / Q000276:immunology
chemical_list: D007252:Influenza Vaccines; D014613:Vaccines, Attenuated
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