title: Assessing the evidence: live attenuated influenza vaccine in children younger than 2 years. A systematic review.
abstract: BACKGROUND
  Live attenuated influenza vaccine (LAIV) is effective in children but contraindicated in children <2 years of age.
  
  
  METHODS
  We searched Medline, EMBASE, the Cochrane Library, Web of Science, Scopus, PsycInfo and CINAHL through February 2013 for existing systematic reviews, randomized controlled trials (RCTs) and observational studies (for safety). We included studies enrolling healthy children <2 years of age who received LAIV, compared with placebo or inactivated influenza vaccine (IIV). Data were extracted independently by 2 investigators. The relative risk (RR) was pooled across studies using the random effects model.
  
  
  RESULTS
  We found 7 eligible randomized controlled trials and 2 observational studies. Randomized controlled trials included 6281 children and were at low to moderate risk of bias. LAIV reduced the incidence of influenza compared with placebo (relative risk = 0.36, 95% confidence interval: 0.23-0.58, P < 0.05) with a number needed to vaccinate of 17. LAIV increased the incidence of minor side effects (fever and rhinorrhea). LAIV had a similar effect in preventing influenza (relative risk = 0.76, 95% confidence interval: 0.45-1.30, P > 0.05) compared with inactivated influenza vaccine. There was an increase of hospitalization rate (post hoc analysis) and medical attended wheezing with LAIV.
  
  
  CONCLUSIONS
  LAIV is highly effective in children <2 years of age compared with placebo and is as effective to inactivated influenza vaccine. The safety profile of LAIV is reasonable although evidence is sparse. LAIV may be considered as an option in this age group particularly during seasons with vaccine shortage.
authors.affiliation: From the *Knowledge and Evaluation Research Unit, Mayo Clinic, Rochester, MN; †Department of Pediatrics, Children's Hospital of Michigan, Wayne State University School of Medicine/Detroit Medical Center, Detroit, MI; ‡Unidad de Conocimiento y Evidencia, Universidad Peruana Cayetano Heredia, Lima, Peru; §Department of Internal Medicine, Henry Ford Hospital, Detroit, MI; and ¶Division of Preventive, Occupational and Aerospace Medicine, Mayo Clinic, MN.
authors.forename: Gabriela J
authors.initials: GJ
authors.lastname: Prutsky
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Domecq
authors.forename: Tarig
authors.initials: T
authors.lastname: Elraiyah
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Prokop
authors.forename: M Hassan
authors.initials: MH
authors.lastname: Murad
mesh_terms: D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D014613:Vaccines, Attenuated / Q000008:administration & dosage
chemical_list: D007252:Influenza Vaccines; D014613:Vaccines, Attenuated