{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T16:21:01Z","timestamp":1788366061265,"version":"build-2803163510"},"reference-count":13,"publisher":"Oxford University Press (OUP)","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,2]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>With declining influenza vaccine coverage since the coronavirus disease (COVID-19) pandemic, it is more critical than ever to provide a strong evidence base to support the benefits of influenza vaccination. Influenza vaccination can reduce the risk of influenza-associated outpatient visits and hospitalizations, and some studies have also shown that influenza vaccination can decrease the severity of disease among those who develop influenza illness despite vaccination. Yet, using observational real-world data to demonstrate these benefits is challenging. In this commentary, we outline some of the challenges and issues to consider when designing observational studies to demonstrate the benefits of influenza vaccination among patients hospitalized with influenza. We further provide suggestions for how to create more standardized definitions for severe and critical influenza outcomes against which vaccine benefits may be measured, using lessons learned from the COVID-19 pandemic.<\/jats:p>","DOI":"10.1093\/cid\/ciag304","type":"journal-article","created":{"date-parts":[[2026,5,7]],"date-time":"2026-05-07T11:43:58Z","timestamp":1778154238000},"page":"e442-e444","source":"Crossref","is-referenced-by-count":0,"title":["Challenges in Defining Severe Influenza With Implications for Measuring and Communicating Influenza Vaccine Effects"],"prefix":"10.1093","volume":"83","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6566-7138","authenticated-orcid":false,"given":"Catherine H","family":"Bozio","sequence":"first","affiliation":[{"name":"Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manish","family":"Patel","sequence":"additional","affiliation":[{"name":"Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7944-7638","authenticated-orcid":false,"given":"Carrie","family":"Reed","sequence":"additional","affiliation":[{"name":"Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9345-6669","authenticated-orcid":false,"given":"Shikha","family":"Garg","sequence":"additional","affiliation":[{"name":"Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,5,7]]},"reference":[{"key":"2026090211590096900_ciag304-B1","volume-title":"Estimated US Flu disease burden","author":"Centers for Disease Control and Prevention","year":"2024"},{"key":"2026090211590096900_ciag304-B2","doi-asserted-by":"crossref","first-page":"942","DOI":"10.1016\/S1473-3099(16)00129-8","article-title":"Variable influenza vaccine effectiveness by subtype: a systematic review and meta-analysis of test-negative design studies","volume":"16","author":"Belongia","year":"2016","journal-title":"Lancet Infect Dis"},{"key":"2026090211590096900_ciag304-B3","volume-title":"Flu burden prevented by vaccination","author":"Centers for Disease Control and Prevention.","year":"2024"},{"key":"2026090211590096900_ciag304-B4","doi-asserted-by":"crossref","first-page":"3678","DOI":"10.1016\/j.vaccine.2021.05.011","article-title":"Does influenza vaccination attenuate the severity of breakthrough infections? A narrative review and recommendations for further research","volume":"39","author":"Ferdinands","year":"2021","journal-title":"Vaccine"},{"key":"2026090211590096900_ciag304-B5","volume-title":"Flu and children","author":"Centers for Disease Control and Prevention","year":"2024"},{"key":"2026090211590096900_ciag304-B6","doi-asserted-by":"crossref","first-page":"3516","DOI":"10.1016\/j.vaccine.2022.04.069","article-title":"Assessing vaccine effectiveness against severe COVID-19 disease caused by omicron variant. Report from a meeting of the World Health Organization","volume":"40","author":"Feikin","year":"2022","journal-title":"Vaccine"},{"key":"2026090211590096900_ciag304-B7","doi-asserted-by":"crossref","first-page":"5460","DOI":"10.1080\/21645515.2021.1990649","article-title":"A literature review of severity scores for adults with influenza or community-acquired pneumonia - implications for influenza vaccines and therapeutics","volume":"17","author":"Adams","year":"2021","journal-title":"Hum Vaccin Immunother"},{"key":"2026090211590096900_ciag304-B8","doi-asserted-by":"crossref","first-page":"e715","DOI":"10.1016\/S2666-5247(21)00180-4","article-title":"Immune-mediated attenuation of influenza illness after infection: opportunities and challenges","volume":"2","author":"Patel","year":"2021","journal-title":"Lancet Microbe"},{"key":"2026090211590096900_ciag304-B9","volume-title":"Living guidance for clinical management of COVID-19","author":"World Health Organization","year":"2023"},{"key":"2026090211590096900_ciag304-B10","doi-asserted-by":"crossref","first-page":"e192","DOI":"10.1016\/S1473-3099(20)30483-7","article-title":"A minimal common outcome measure set for COVID-19 clinical research","volume":"20","author":"WHO Working Group on the Clinical Characterisation and Management of COVID-19 infection","year":"2020","journal-title":"Lancet Infect Dis"},{"key":"2026090211590096900_ciag304-B11","doi-asserted-by":"crossref","first-page":"103207","DOI":"10.1016\/j.eclinm.2025.103207","article-title":"Identification and characterisation of clinically distinct subgroups of adults hospitalised with influenza in the USA: a repeated cross-sectional study","volume":"83","author":"Bozio","year":"2025","journal-title":"EClinicalMedicine"},{"key":"2026090211590096900_ciag304-B12","volume-title":"Flu vaccination coverage, United States, 2024-25 influenza season","author":"Centers for Disease Control and Prevention","year":"2026"},{"key":"2026090211590096900_ciag304-B13","doi-asserted-by":"crossref","first-page":"2496","DOI":"10.1093\/cid\/ciz676","article-title":"Projected population benefit of increased effectiveness and coverage of influenza vaccination on influenza burden in the United States","volume":"70","author":"Hughes","year":"2020","journal-title":"Clin Infect Dis"}],"container-title":["Clinical Infectious Diseases"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/cid\/advance-article-pdf\/doi\/10.1093\/cid\/ciag304\/68246850\/ciag304.pdf","content-type":"application\/pdf","content-version":"am","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/cid\/article-pdf\/83\/2\/e442\/68246850\/ciag304.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/cid\/article-pdf\/83\/2\/e442\/68246850\/ciag304.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T15:59:08Z","timestamp":1788364748000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/cid\/article\/83\/2\/e442\/8672549"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,7]]},"references-count":13,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,5,7]]},"published-print":{"date-parts":[[2026,9,2]]}},"URL":"https:\/\/doi.org\/10.1093\/cid\/ciag304","relation":{},"ISSN":["1058-4838","1537-6591"],"issn-type":[{"value":"1058-4838","type":"print"},{"value":"1537-6591","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026,8,15]]},"published":{"date-parts":[[2026,5,7]]}}}