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. 2023 Jul 14;228(2):185-195.
doi: 10.1093/infdis/jiad015.

Vaccine Effectiveness Against Influenza-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2021-2022 Season, VISION Network

Mark W Tenforde  1 , Zachary A Weber  2 , Malini B DeSilva  3 , Edward Stenehjem  4 , Duck-Hye Yang  2 , Bruce Fireman  5 , Manjusha Gaglani  6   7 , Noah Kojima  1 , Stephanie A Irving  8 , Suchitra Rao  9 , Shaun J Grannis  10   11 , Allison L Naleway  8 , Lindsey Kirshner  2 , Anupam B Kharbanda  12 , Kristin Dascomb  4 , Ned Lewis  5 , Alexandra F Dalton  1 , Sarah W Ball  2 , Karthik Natarajan  13   14 , Toan C Ong  9 , Emily Hartmann  15 , Peter J Embi  10   16 , Charlene E McEvoy  3 , Nancy Grisel  4 , Ousseny Zerbo  5 , Margaret M Dunne  2 , Julie Arndorfer  4 , Kristin Goddard  5 , Monica Dickerson  1 , Palak Patel  1 , Julius Timbol  5 , Eric P Griggs  1 , John Hansen  5 , Mark G Thompson  1 , Brendan Flannery  1 , Nicola P Klein  5
Affiliations

Vaccine Effectiveness Against Influenza-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2021-2022 Season, VISION Network

Mark W Tenforde et al. J Infect Dis. .

Abstract

Background: Following historically low influenza activity during the 2020-2021 season, the United States saw an increase in influenza circulating during the 2021-2022 season. Most viruses belonged to the influenza A(H3N2) 3C.2a1b 2a.2 subclade.

Methods: We conducted a test-negative case-control analysis among adults ≥18 years of age at 3 sites within the VISION Network. Encounters included emergency department/urgent care (ED/UC) visits or hospitalizations with ≥1 acute respiratory illness (ARI) discharge diagnosis codes and molecular testing for influenza. Vaccine effectiveness (VE) was calculated by comparing the odds of influenza vaccination ≥14 days before the encounter date between influenza-positive cases (type A) and influenza-negative and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative controls, applying inverse probability-to-be-vaccinated weights, and adjusting for confounders.

Results: In total, 86 732 ED/UC ARI-associated encounters (7696 [9%] cases) and 16 805 hospitalized ARI-associated encounters (649 [4%] cases) were included. VE against influenza-associated ED/UC encounters was 25% (95% confidence interval (CI), 20%-29%) and 25% (95% CI, 11%-37%) against influenza-associated hospitalizations. VE against ED/UC encounters was lower in adults ≥65 years of age (7%; 95% CI, -5% to 17%) or with immunocompromising conditions (4%; 95% CI, -45% to 36%).

Conclusions: During an influenza A(H3N2)-predominant influenza season, modest VE was observed. These findings highlight the need for improved vaccines, particularly for A(H3N2) viruses that are historically associated with lower VE.

Keywords: COVID-19; bias; influenza; test-negative design; vaccine effectiveness.

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Conflict of interest statement

Potential conflicts of interest. S. R. received grants from GlaxoSmithKline. A. L. N. received grants from Pfizer and Vir Biotechnology. C. M. received grants from AstraZeneca. N. P. K. received grants from Pfizer, Merck, GlaxoSmithKline, and Sanofi Pasteur. 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 vaccine effectiveness against emergency department- or urgent care-associated influenza illness. Abbreviations: CI, confidence interval; Col, column; VE, vaccine effectiveness.
Figure 2.
Figure 2.
Influenza vaccine effectiveness against hospitalized influenza illness. Abbreviations: CI, confidence interval; Col, column; VE, vaccine effectiveness.
See this image and copyright information in PMC

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