Effectiveness of live attenuated influenza vaccine and inactivated influenza vaccine in children during the 2014-2015 season

Vaccine. 2017 May 9;35(20):2685-2693. doi: 10.1016/j.vaccine.2017.03.085. Epub 2017 Apr 10.


Background: A clinical study found that live attenuated influenza vaccine (LAIV) was superior to inactivated influenza vaccine (IIV) against drifted A(H3N2) viruses in children. During the 2014-2015 influenza season, widespread circulation of antigenically and genetically drifted A(H3N2) viruses provided an opportunity to evaluate subtype-specific vaccine effectiveness (VE) of quadrivalent LAIV (LAIV4) and IIV in children.

Methods: Children (2-17years) with febrile acute respiratory illness <5days' duration were enrolled at 4 outpatient sites in the United States during the 2014-2015 influenza season. Nasal swabs were tested for influenza by reverse transcription polymerase chain reaction; vaccination dates were obtained from medical records or immunization registries. VE was estimated using a test-negative design comparing odds of vaccination among influenza cases and test-negative controls with adjustment for potential confounders.

Results: Among 1696 children enrolled, 1511 (89%) were included in the analysis. Influenza was detected in 427 (28%) children; 317 had influenza A(H3N2) and 110 had influenza B. Most influenza isolates were characterized as a drifted strain of influenza A(H3N2) or a drifted strain of B/Yamagata. For LAIV4, adjusted VE was 50% (95% confidence interval [CI], 27-66%) against any influenza, 30% (95% CI, -6% to 54%) against influenza A(H3N2), and 87% (95% CI, 63-96%) against type B. For IIV, adjusted VE was 39% (95% CI, 18-54%) against any influenza, 40% (95% CI, 16-58%) against A(H3N2), and 29% (95% CI, -15% to 56%) against type B. Odds of influenza for LAIV4 versus IIV recipients were similar against influenza A(H3N2) (odds ratio [OR], 1.17; 95% CI, 0.73-1.86) and lower against influenza B (OR, 0.18; 95% CI, 0.06-0.55).

Conclusions: LAIV4 and IIV provided similar protection against a new antigenic variant A(H3N2). LAIV4 provided significantly greater protection than IIV against a drifted influenza B strain. ClinicalTrials.gov identifier: NCT01997450.

Keywords: Influenza; Influenza vaccine; Pediatrics; Vaccine effectiveness.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Influenza A Virus, H3N2 Subtype / immunology*
  • Influenza A Virus, H3N2 Subtype / isolation & purification
  • Influenza B virus / immunology*
  • Influenza B virus / isolation & purification
  • Influenza Vaccines / administration & dosage
  • Influenza Vaccines / immunology*
  • Influenza, Human / prevention & control*
  • Male
  • Pharynx / virology
  • Treatment Outcome
  • United States
  • Vaccines, Attenuated / administration & dosage
  • Vaccines, Attenuated / immunology
  • Vaccines, Inactivated / administration & dosage
  • Vaccines, Inactivated / immunology


  • Influenza Vaccines
  • Vaccines, Attenuated
  • Vaccines, Inactivated

Associated data

  • ClinicalTrials.gov/NCT01997450