Influenza Vaccine Effectiveness Among Children: 2011-2020

Pediatrics. 2023 Apr 1;151(4):e2022059922. doi: 10.1542/peds.2022-059922.


Background and objectives: Infants and children are at increased risk of severe influenza virus infection and its complications. Influenza vaccine effectiveness (VE) varies by age, influenza season, and influenza virus type/subtype. This study's objective was to examine the effectiveness of inactivated influenza vaccine against outpatient influenza illness in the pediatric population over 9 influenza seasons after the 2009 A(H1N1) pandemic.

Methods: During the 2011-2012 through the 2019-2020 influenza seasons at outpatient clinics at 5 sites of the US Influenza Vaccine Effectiveness Network, children aged 6 months to 17 years with an acute respiratory illness were tested for influenza using real-time, reverse-transcriptase polymerase chain reaction. Vaccine effectiveness was estimated using a test-negative design.

Results: Among 24 148 enrolled children, 28% overall tested positive for influenza, 3017 tested positive for influenza A(H3N2), 1459 for influenza A(H1N1)pdm09, and 2178 for influenza B. Among all enrollees, 39% overall were vaccinated, with 29% of influenza cases and 43% of influenza-negative controls vaccinated. Across all influenza seasons, the pooled VE for any influenza was 46% (95% confidence interval, 43-50). Overall and by type/subtype, VE against influenza illness was highest among children in the 6- to 59-month age group compared with older pediatric age groups. VE was lowest for influenza A(H3N2) virus infection.

Conclusions: Analysis of multiple seasons suggested substantial benefit against outpatient illness. Investigation of host-specific or virus-related mechanisms that may result in differences by age and virus type/subtype may help further efforts to promote increased vaccination coverage and other influenza-related preventative measures.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Case-Control Studies
  • Child
  • Child, Preschool
  • Humans
  • Infant
  • Influenza A Virus, H1N1 Subtype*
  • Influenza A Virus, H3N2 Subtype
  • Influenza B virus
  • Influenza Vaccines* / therapeutic use
  • Influenza, Human* / epidemiology
  • Influenza, Human* / prevention & control
  • Seasons
  • Vaccination
  • Vaccine Efficacy
  • Vaccines, Inactivated


  • Influenza Vaccines
  • Vaccines, Inactivated