Vaccine Effectiveness Against Influenza A(H1N1), A(H3N2), and B-Associated Hospitalizations-United States, September 1, 2023-May 31, 2024

Nathaniel M Lewis¹, Elizabeth J Harker¹, Seana Cleary¹, Yuwei Zhu², Carlos G Grijalva², James D Chappell², Jillian P Rhoads², Adrienne Baughman², Jonathan D Casey², Paul W Blair², Ian D Jones², Cassandra A Johnson², Natasha B Halasa², Adam S Lauring³, Emily T Martin³, Manju Gaglani^{4

5}, Shekhar Ghamande⁵, Cristie Columbus^{5

6}, Jay S Steingrub⁷, Abhijit Duggal⁸, Jamie R Felzer⁹, Matthew E Prekker¹⁰, Ithan D Peltan^{11

12}, Samuel M Brown^{11

12}, David N Hager¹³, Michelle N Gong¹⁴, Amira Mohamed¹⁴, Matthew C Exline¹⁵, Akram Khan¹⁶, Samantha A N Ferguson¹⁷, Jarrod Mosier¹⁸, Nida Qadir¹⁹, Steven Y Chang¹⁹, Adit A Ginde²⁰, Anne Zepeski²¹, Christopher Mallow²², Estelle S Harris¹¹, Nicholas J Johnson²³, Kevin W Gibbs²⁴, Jennie H Kwon²⁵, Ivana A Vaughn²⁶, Mayur Ramesh²⁶, Basmah Safdar²⁷, Diya Surie²⁸, Fatimah S Dawood²⁸, Sascha Ellington¹, Wesley H Self²

Affiliations

¹ Influenza Division, CDC, Atlanta Georgia, USA.
² Vanderbilt University Medical Center, Nashville, Tennessee, USA.
³ University of Michigan, Ann Arbor, Michigan, USA.
⁴ Baylor Scott & White Health, Temple, Texas, USA.
⁵ Baylor College of Medicine, Temple, Texas, USA.
⁶ Texas A&M University College of Medicine, Dallas, Texas, USA.
⁷ Baystate Medical Center, Springfield, Massachusetts, USA.
⁸ Cleveland Clinic, Cleveland, Ohio, USA.
⁹ Emory University, Atlanta, Georgia, USA.
¹⁰ Hennepin County Medical Center, Minneapolis, Minnesota, USA.
¹¹ University of Utah, Salt Lake City, Utah, USA.
¹² Intermountain Medical Center, Murray, Utah; University of Utah, Salt Lake City, Utah, USA.
¹³ Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
¹⁴ Montefiore Medical Center, Albert Einstein College of Medicine, New York, New York, USA.
¹⁵ The Ohio State University, Columbus, Ohio, USA.
¹⁶ Oregon Health & Science University, Portland, Oregon, USA.
¹⁷ Stanford University School of Medicine, Stanford, California, USA.
¹⁸ University of Arizona, Tucson, Arizona, USA.
¹⁹ Ronald Reagan UCLA Medical Center, Los Angeles, California, USA.
²⁰ University of Colorado School of Medicine, Aurora, Colorado, USA.
²¹ Carver College of Medicine, Iowa City, Iowa, USA.
²² University of Miami School of Medicine, Miami, Florida, USA.
²³ University of Washington, Seattle, Washington, USA.
²⁴ Wake Forest School of Medicine, Winston-Salem, North Carolina, USA.
²⁵ Washington University in St. Louis, St. Louis, Missouri, USA.
²⁶ Henry Ford Health, Detroit, Michigan, USA.
²⁷ Yale University School of Medicine, New Haven, Connecticut, USA.
²⁸ Division of COVID-19 and Other Respiratory Viral Diseases, CDC, Atlanta, Georgia, USA.

PMID: 40198276
DOI: 10.1093/infdis/jiaf185

Vaccine Effectiveness Against Influenza A(H1N1), A(H3N2), and B-Associated Hospitalizations-United States, September 1, 2023-May 31, 2024

Nathaniel M Lewis et al. J Infect Dis. 2025.

. 2025 Apr 8:jiaf185.

doi: 10.1093/infdis/jiaf185. Online ahead of print.

Authors

Affiliations

¹ Influenza Division, CDC, Atlanta Georgia, USA.
² Vanderbilt University Medical Center, Nashville, Tennessee, USA.
³ University of Michigan, Ann Arbor, Michigan, USA.
⁴ Baylor Scott & White Health, Temple, Texas, USA.
⁵ Baylor College of Medicine, Temple, Texas, USA.
⁶ Texas A&M University College of Medicine, Dallas, Texas, USA.
⁷ Baystate Medical Center, Springfield, Massachusetts, USA.
⁸ Cleveland Clinic, Cleveland, Ohio, USA.
⁹ Emory University, Atlanta, Georgia, USA.
¹⁰ Hennepin County Medical Center, Minneapolis, Minnesota, USA.
¹¹ University of Utah, Salt Lake City, Utah, USA.
¹² Intermountain Medical Center, Murray, Utah; University of Utah, Salt Lake City, Utah, USA.
¹³ Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
¹⁴ Montefiore Medical Center, Albert Einstein College of Medicine, New York, New York, USA.
¹⁵ The Ohio State University, Columbus, Ohio, USA.
¹⁶ Oregon Health & Science University, Portland, Oregon, USA.
¹⁷ Stanford University School of Medicine, Stanford, California, USA.
¹⁸ University of Arizona, Tucson, Arizona, USA.
¹⁹ Ronald Reagan UCLA Medical Center, Los Angeles, California, USA.
²⁰ University of Colorado School of Medicine, Aurora, Colorado, USA.
²¹ Carver College of Medicine, Iowa City, Iowa, USA.
²² University of Miami School of Medicine, Miami, Florida, USA.
²³ University of Washington, Seattle, Washington, USA.
²⁴ Wake Forest School of Medicine, Winston-Salem, North Carolina, USA.
²⁵ Washington University in St. Louis, St. Louis, Missouri, USA.
²⁶ Henry Ford Health, Detroit, Michigan, USA.
²⁷ Yale University School of Medicine, New Haven, Connecticut, USA.
²⁸ Division of COVID-19 and Other Respiratory Viral Diseases, CDC, Atlanta, Georgia, USA.

PMID: 40198276
DOI: 10.1093/infdis/jiaf185

Abstract

Background: The 2023-2024 influenza season included sustained elevated activity from December 2023-February 2024 and continued activity through May 2024. Influenza A(H1N1), A(H3N2), and B viruses circulated during the season.

Methods: During September 1, 2023-May 31, 2024, a multistate sentinel surveillance network of 24 medical centers in 20 U.S. states enrolled adults aged ≥18 years hospitalized with acute respiratory illness (ARI). Consistent with a test-negative design, cases tested positive for influenza viruses by molecular or antigen test, and controls tested negative for influenza viruses and SARS-CoV-2. Vaccine effectiveness (VE) against influenza-associated hospitalization was calculated as (1 - adjusted odds ratio for vaccination) × 100%.

Results: Among 7690 patients, including 1170 influenza cases (33% vaccinated) and 6520 controls, VE was 40% (95% CI: 31%-48%) with varying estimates by age (18-49 years: 53% [34%-67%]; 50-64 years: 47% [31%-60%]; ≥65 years: 31% [16%-43%]). Protection was similar among immunocompetent patients (40% [30%-49%]) and immunocompromised patients (32% [7-50%]). VE was statistically significant against influenza B (67% [35%-84%]) and A(H1N1) (36% [21%-48%]) and crossed the null against A(H3N2) (19% [-8%-39%]). VE was higher for patients 14-60 days from vaccination (54% [40%-65%]) than >120 days (18% [-1%-33%]).

Conclusions: During 2023-2024, influenza vaccination reduced the risk of influenza A(H1N1)- and influenza B-associated hospitalizations among adults; effectiveness was lower in patients vaccinated >120 days prior to illness onset compared with those vaccinated 14-60 days prior.

Keywords: hospitalization; seasonal influenza; severe influenza; vaccine effectiveness; waning.

Published by Oxford University Press on behalf of Infectious Diseases Society of America 2025.

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Vaccine Effectiveness Against Influenza A(H1N1), A(H3N2), and B-Associated Hospitalizations-United States, September 1, 2023-May 31, 2024

Affiliations

Vaccine Effectiveness Against Influenza A(H1N1), A(H3N2), and B-Associated Hospitalizations-United States, September 1, 2023-May 31, 2024

Authors

Affiliations

Abstract

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Full Text Sources

Miscellaneous