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. 2024 Mar 20;78(3):746-755.
doi: 10.1093/cid/ciad704.

Vaccine Effectiveness Against Pediatric Influenza-A-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2022-2023 Season: VISION Network

Katherine Adams  1 , Zachary A Weber  2 , Duck-Hye Yang  2 , Nicola P Klein  3 , Malini B DeSilva  4 , Kristin Dascomb  5 , Stephanie A Irving  6 , Allison L Naleway  6 , Suchitra Rao  7 , Manjusha Gaglani  8   9 , Brendan Flannery  1 , Shikha Garg  1 , Anupam B Kharbanda  10 , Shaun J Grannis  11   12 , Toan C Ong  13 , Peter J Embi  14 , Karthik Natarajan  15   16 , Bruce Fireman  3 , Ousseny Zerbo  3 , Kristin Goddard  3 , Julius Timbol  3 , John R Hansen  3 , Nancy Grisel  5 , Julie Arndorfer  5 , Sarah W Ball  2 , Margaret M Dunne  2 , Lindsey Kirshner  2 , Jessie R Chung  1 , Mark W Tenforde  1
Affiliations

Vaccine Effectiveness Against Pediatric Influenza-A-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2022-2023 Season: VISION Network

Katherine Adams et al. Clin Infect Dis. .

Abstract

Background: During the 2022-2023 influenza season, the United States experienced the highest influenza-associated pediatric hospitalization rate since 2010-2011. Influenza A/H3N2 infections were predominant.

Methods: We analyzed acute respiratory illness (ARI)-associated emergency department or urgent care (ED/UC) encounters or hospitalizations at 3 health systems among children and adolescents aged 6 months-17 years who had influenza molecular testing during October 2022-March 2023. We estimated influenza A vaccine effectiveness (VE) using a test-negative approach. The odds of vaccination among influenza-A-positive cases and influenza-negative controls were compared after adjusting for confounders and applying inverse-propensity-to-be-vaccinated weights. We developed overall and age-stratified VE models.

Results: Overall, 13 547 of 44 787 (30.2%) eligible ED/UC encounters and 263 of 1862 (14.1%) hospitalizations were influenza-A-positive cases. Among ED/UC patients, 15.2% of influenza-positive versus 27.1% of influenza-negative patients were vaccinated; VE was 48% (95% confidence interval [CI], 44-52%) overall, 53% (95% CI, 47-58%) among children aged 6 months-4 years, and 38% (95% CI, 30-45%) among those aged 9-17 years. Among hospitalizations, 17.5% of influenza-positive versus 33.4% of influenza-negative patients were vaccinated; VE was 40% (95% CI, 6-61%) overall, 56% (95% CI, 23-75%) among children ages 6 months-4 years, and 46% (95% CI, 2-70%) among those 5-17 years.

Conclusions: During the 2022-2023 influenza season, vaccination reduced the risk of influenza-associated ED/UC encounters and hospitalizations by almost half (overall VE, 40-48%). Influenza vaccination is a critical tool to prevent moderate-to-severe influenza illness in children and adolescents.

Keywords: influenza; pediatric; test-negative design; vaccine effectiveness.

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Conflict of interest statement

Potential conflicts of interest . N. P. K. reports research support from Sanofi Pasteur and Seqirus for unrelated adult influenza vaccine effectiveness studies, and from Pfizer, Merck, and GlaxoSmithKline for unrelated studies. S. R. received funds from GlaxoSmithKline. M. G. reports a research grant and contract for the CDC Ambulatory US Flu/COVID VE Network, a grant for HAIVEN Adult Inpatient Flu/COVID VE, a contract for SYNERGY FLU/COVID study, and subcontracts for the IVY COVID/FLU VE PHS project and RECOVER-PROTECT COVID Cohort studies. D.-H. Y., L. K., M. M. D., S. W. B., and Z. A. W. report payments made to Westat via CDC contract number 200-2019-F-06819. A. B. K., A. L. N., J. A., K. D., K. N., M. B. D., M. G., N. G., P. J. E., S. A. I, S. J. G., S. R., and T. C. O. report payments made to their institution by CDC via Westat. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Influenza VE against influenza-A–associated ED or UC visits among children and adolescents 6 months–17 years of age, October 2022–March 2023. Abbreviations: CI, confidence interval; ED, emergency department; UC, urgent care; VE, vaccine effectiveness. aAdjusted for age (natural cubic spline), study site, and date of encounter (natural cubic splines) and applied inverse-probability-to-be-vaccinated weights.
Figure 2.
Figure 2.
Influenza VE against influenza-A–associated hospitalizations among children and adolescents 6 months–17 years of age, October 2022–February 2023. Abbreviations: CI, confidence interval; VE, vaccine effectiveness. aAdjusted for age (natural cubic spline), study site, and date of encounter (natural cubic splines) and applied inverse-probability-to-be-vaccinated weights.
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