Late-Season Influenza Vaccine Effectiveness Against Medically Attended Outpatient Illness, United States, December 2022-April 2023

Influenza Other Respir Viruses. 2024 Jun;18(6):e13342. doi: 10.1111/irv.13342.

Abstract

Background: The 2022-23 US influenza season peaked early in fall 2022.

Methods: Late-season influenza vaccine effectiveness (VE) against outpatient, laboratory-confirmed influenza was calculated among participants of the US Influenza VE Network using a test-negative design.

Results: Of 2561 participants enrolled from December 12, 2022 to April 30, 2023, 91 laboratory-confirmed influenza cases primarily had A(H1N1)pdm09 (6B.1A.5a.2a.1) or A(H3N2) (3C.2a1b.2a.2b). Overall, VE was 30% (95% confidence interval -9%, 54%); low late-season activity precluded estimation for most subgroups.

Conclusions: 2022-23 late-season outpatient influenza VE was not statistically significant. Genomic characterization may improve the identification of influenza viruses that circulate postinfluenza peak.

Keywords: influenza; vaccination; vaccine effectiveness.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Influenza A Virus, H1N1 Subtype* / genetics
  • Influenza A Virus, H1N1 Subtype* / immunology
  • Influenza A Virus, H3N2 Subtype* / genetics
  • Influenza A Virus, H3N2 Subtype* / immunology
  • Influenza Vaccines* / administration & dosage
  • Influenza Vaccines* / immunology
  • Influenza, Human* / epidemiology
  • Influenza, Human* / immunology
  • Influenza, Human* / prevention & control
  • Influenza, Human* / virology
  • Male
  • Middle Aged
  • Outpatients* / statistics & numerical data
  • Seasons*
  • United States / epidemiology
  • Vaccination / statistics & numerical data
  • Vaccine Efficacy*
  • Young Adult

Substances

  • Influenza Vaccines