Influenza vaccine effectiveness against hospitalizations and emergency department or urgent care encounters for children, adolescents, and adults during the 2023-2024 season, United States
- PMID: 39656838
- PMCID: PMC12287760
- DOI: 10.1093/cid/ciae597
Influenza vaccine effectiveness against hospitalizations and emergency department or urgent care encounters for children, adolescents, and adults during the 2023-2024 season, United States
Abstract
Background: The 2023-2024 influenza season had predominant influenza A(H1N1)pdm09 virus activity, but A(H3N2) and B viruses co-circulated. Seasonal influenza vaccine strains were well-matched to these viruses.
Methods: Using health care encounters data from health systems in 8 states, we evaluated influenza vaccine effectiveness (VE) against influenza-associated medical encounters from October 2023-April 2024. Using a test-negative design, we compared the odds of vaccination between patients with an acute respiratory illness (ARI) who tested positive (cases) versus negative (controls) for influenza by molecular assay, adjusting for confounders. VE was stratified by age group, influenza type (overall, influenza A, influenza B), and care setting (hospitalization, emergency department or urgent care [ED/UC] encounter).
Results: Overall, 74,000 encounters in children and adolescents aged 6 months - 17 years (3,479 hospitalizations, 70,521 ED/UC encounters) and 267,606 in adults aged ≥18 years (66,828 hospitalizations, 200,778 ED/UC encounters) were included. Across care settings, among children and adolescents 15% (2,758/17,833) of cases versus 32% (18,240/56,167) of controls had received vaccination. Among adults, 25% (11,632/46,614) of cases versus 44% (97,811/220,992) of controls across care settings had received vaccination. VE was 58% (95% confidence interval [95% CI]: 44-69%) against hospitalization and 58% (95% CI: 56-60%) against ED/UC encounters for children and adolescents, and 39% (95% CI: 35-43) against hospitalization and 47% (95% CI: 46-49%) against ED/UC encounters for adults. Across age groups, VE was higher against influenza B than influenza A.
Conclusions: Influenza vaccines provided protection against influenza-associated illness across health care settings and age groups during the 2023-2024 influenza season.
Keywords: influenza; test-negative design; vaccination; vaccine effectiveness.
Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.
Conflict of interest statement
All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. During the conduct of the study, all Kaiser Permanente Southern California Department of Research and Evaluation and Kaiser Permanente Northern California Division of Research-affiliated authors reported receiving contractual support from the Centers for Disease Control and Prevention (CDC) via payments made to their respective institutions. Additionally, all authors affiliated with HealthPartners Institute, Intermountain Healthcare, Kaiser Permanente Center for Health Research, Regenstrief Institute, and University of Colorado Anschutz Medical Campus reported receiving contractual support from the CDC during the conduct of the study, via subcontracts from Westat, Inc. with payments made to their respective institutions. Unrelated to the submitted work, the following disclosures were reported from the past 36 months: SYT reports contracts from GlaxoSmithKline and Pfizer. NPK reports support from Sanofi Pasteur, Merck, Pfizer, Seqirus, and GlaxoSmithKline. TCO received consulting fees from Regenstrief Institute and support for travel from Patient-Centered Outcomes Research Institute (PCORI) and Regenstrief Institute and has a current patent, PCT/US2018/047961. SJG reports contracts with National Institutes of Health (NIH) National Center for Advancing Translational Sciences and NIH National Institute of Mental Health. BED reports a contract with Vaccine Safety Datalink Project, Contract No. 75D30122D15424. WFF reports a contract with Vaccine Safety Datalink Project, Contract No. 75D30122D15424. CEM reports support from NIH, Department of Defense, PCORI, Astra Zeneca, and GlaxoSmithKline and is a member of the American Lung Association of Minnesota Board, Minnesota Department of Health Long COVID Advisory Committee, and Minnesota Department of Health Asthma Care Advisory Committee. TS is a member of CDC Advisory Committee on Immunization Practices Influenza Vaccine Work Group, chair of Utah Adult Immunization Coalition – volunteer vaccine quality improvement and advocacy group and a member of Utah Department of Health and Human Services Scientific Advisory Committee on Vaccines. OZ reports contract number R01AI168373 with the National Institute of Allergy and Infectious Diseases. LSS reports contracts with GlaxoSmithKline, Moderna, and Dynavax. SR reports support from Biofire and GlaxoSmithKline. MB was a speaker bureau participant – Innoviva Specialty Therapeutics -Oct 2023. No other disclosures were reported.
Figures




References
-
- Centers for Disease Control and Prevention. Preliminary Estimated Flu Disease Burden 2023–2024 Flu Season. Available at: https://www.cdc.gov/flu-burden/php/data-vis/2023-2024.html. Accessed on: 27 Sept 2024.
-
- Centers for Disease Control and Prevention. FluView Interactive: Laboratory-confirmed influenza hospitalizations. Available at: https://gis.cdc.gov/GRASP/Fluview/FluHospRates.html. Accessed on: 2 Jul 2024.
-
- Centers for Disease Control and Prevention. Weekly U.S. Influenza Surveillance Report. Available at: https://www.cdc.gov/flu/weekly/index.htm. Accessed on: 2 Jul 2024.
-
- Centers for Disease Control and Prevention. Health Alert Network: Urgent Need to Increase Immunization Coverage for Influenza, COVID-19, and RSV and Use of Authorized/Approved Therapeutics in the Setting of Increased Respiratory Disease Activity During the 2023 – 2024 Winter Season. Available at: https://emergency.cdc.gov/han/2023/han00503.asp. Accessed on: 19 Jul 2024.
Grants and funding
LinkOut - more resources
Full Text Sources
Miscellaneous