title: Efficacy of live attenuated influenza vaccine against influenza illness in children as a function of illness severity.
abstract: A recent study of inactivated influenza vaccine (IIV) in children aged 3-8 years demonstrated higher efficacy against moderate/severe influenza. A meta-analysis of all previous published randomized clinical trials of live attenuated influenza vaccine (LAIV) that collected information on illness severity in children aged 24-71 months was conducted. Moderate/severe influenza was defined as fever >39°C, acute otitis media, or lower respiratory tract illness; other cases were classified as milder influenza. LAIV efficacy versus placebo was 95.4% [95% confidence interval: 88.5, 98.1] (year 1) and 88.5% [77.4, 94.9] (year 2) against moderate/severe influenza and 91.4% [77.9, 96.7] (year 1) and 84.2% [56.7, 94.3] (year 2) against milder influenza. The relative efficacy of LAIV versus IIV was 52.2% [31.6, 66.6] for moderate/severe influenza and 45.0% [28.6, 57.5] for milder influenza. Efficacy against all influenza illnesses, regardless of severity, is critical to prevent influenza illness and transmission in the community.
authors.affiliation: AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA. Electronic address: ambrosec@medimmune.com.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Ambrose
authors.affiliation: MedImmune, One MedImmune Way, Gaithersburg, MD 20878, USA. Electronic address: wilson.wu.xionghua@gmail.com.
authors.forename: Xionghua
authors.initials: X
authors.lastname: Wu
authors.affiliation: AstraZeneca, One MedImmune Way, Gaithersburg, MD 20878, USA. Electronic address: caspardh@medimmune.com.
authors.forename: Herve
authors.initials: H
authors.lastname: Caspard
authors.affiliation: Saint Louis University Medical Center, 1100 S. Grand Blvd., DRC-8th Floor, St. Louis, MO 63104, USA. Electronic address: belsherb@slu.edu.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Belshe
mesh_terms: D002648:Child; D002675:Child, Preschool; D006801:Humans; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic; D012720:Severity of Illness Index; D014613:Vaccines, Attenuated / Q000627:therapeutic use
chemical_list: D007252:Influenza Vaccines; D014613:Vaccines, Attenuated
keywords: Disease severity; Influenza; Live attenuated influenza vaccine