{"doi":"10.1093/cid/ciab462","title":"Influenza Vaccine Effectiveness for Prevention of Severe Influenza-Associated Illness Among Adults in the United States, 2019–2020: A Test-Negative Study","abstract":"BACKGROUND: Influenza vaccine effectiveness (VE) against a spectrum of severe disease, including critical illness and death, remains poorly characterized. METHODS: We conducted a test-negative study in an intensive care unit (ICU) network at 10 US hospitals to evaluate VE for preventing influenza-associated severe acute respiratory infection (SARI) during the 2019-2020 season, which was characterized by circulation of drifted A/H1N1 and B-lineage viruses. Cases were adults hospitalized in the ICU and a targeted number outside the ICU (to capture a spectrum of severity) with laboratory-confirmed, influenza-associated SARI. Test-negative controls were frequency-matched based on hospital, timing of admission, and care location (ICU vs non-ICU). Estimates were adjusted for age, comorbidities, and other confounders. RESULTS: Among 638 patients, the median (interquartile) age was 57 (44-68) years; 286 (44.8%) patients were treated in the ICU and 42 (6.6%) died during hospitalization. Forty-five percent of cases and 61% of controls were vaccinated, which resulted in an overall VE of 32% (95% CI: 2-53%), including 28% (-9% to 52%) against influenza A and 52% (13-74%) against influenza B. VE was higher in adults 18-49 years old (62%; 95% CI: 27-81%) than those aged 50-64 years (20%; -48% to 57%) and ≥65 years old (-3%; 95% CI: -97% to 46%) (P = .0789 for interaction). VE was significantly higher against influenza-associated death (80%; 95% CI: 4-96%) than nonfatal influenza illness. CONCLUSIONS: During a season with drifted viruses, vaccination reduced severe influenza-associated illness among adults by 32%. VE was high among young adults.","journal":"Clinical Infectious Diseases","year":2021,"id":167876,"datarank":0.5289540786924243,"base_score":3.5263605246161616,"endowment":3.5263605246161616,"self_citation_contribution":0.5289540786924243,"citation_network_contribution":0.0,"self_endowment_contribution":0.5289540786924243,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":33,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9578,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":106003,"name":"Leora R. Feldstein","orcid":"0000-0002-4430-6760","position":1,"is_corresponding":false},{"id":105916,"name":"H. Keipp Talbot","orcid":"0000-0003-0141-1760","position":2,"is_corresponding":false},{"id":105989,"name":"Michael S. Aboodi","orcid":null,"position":3,"is_corresponding":false},{"id":244031,"name":"Adrienne Baughman","orcid":null,"position":4,"is_corresponding":false},{"id":105995,"name":"Samuel M. Brown","orcid":"0000-0003-1206-6261","position":5,"is_corresponding":false},{"id":242316,"name":"Jonathan D. Casey","orcid":"0000-0002-0977-290X","position":6,"is_corresponding":false},{"id":105985,"name":"Heidi L. Erickson","orcid":"0000-0001-5537-8893","position":7,"is_corresponding":false},{"id":105990,"name":"Matthew C. Exline","orcid":"0000-0001-6797-158X","position":8,"is_corresponding":false},{"id":105983,"name":"D. Clark Files","orcid":"0000-0002-1595-4080","position":9,"is_corresponding":false},{"id":105984,"name":"Kevin W. Gibbs","orcid":"0000-0002-5272-2289","position":10,"is_corresponding":false},{"id":105999,"name":"Adit A. Ginde","orcid":"0000-0003-2325-206X","position":11,"is_corresponding":false},{"id":105988,"name":"Michelle N. Gong","orcid":"0000-0001-7952-5384","position":12,"is_corresponding":false},{"id":105913,"name":"Natasha Halasa","orcid":"0000-0002-6381-1826","position":13,"is_corresponding":false},{"id":105993,"name":"Akram Khan","orcid":"0000-0003-3091-632X","position":14,"is_corresponding":false},{"id":105980,"name":"Christopher J. Lindsell","orcid":"0000-0002-3297-2811","position":15,"is_corresponding":false},{"id":482082,"name":"Samuel Nwosu","orcid":null,"position":16,"is_corresponding":false},{"id":105996,"name":"Ithan D. Peltan","orcid":"0000-0003-1730-234X","position":17,"is_corresponding":false},{"id":242315,"name":"Matthew E. Prekker","orcid":"0000-0002-3969-3022","position":18,"is_corresponding":false},{"id":105997,"name":"Todd W. Rice","orcid":"0000-0002-7136-5408","position":19,"is_corresponding":false},{"id":105982,"name":"Nathan I. Shapiro","orcid":"0000-0003-3508-4390","position":20,"is_corresponding":false},{"id":105986,"name":"Jay S. Steingrub","orcid":"0000-0002-6019-6725","position":21,"is_corresponding":false},{"id":106000,"name":"William B. Stubblefield","orcid":"0000-0003-3817-1414","position":22,"is_corresponding":false},{"id":105978,"name":"Mark W. Tenforde","orcid":"0000-0002-8702-8393","position":23,"is_corresponding":false},{"id":242318,"name":"Manish M. Patel","orcid":"0000-0001-8949-6548","position":24,"is_corresponding":false},{"id":106002,"name":"Wesley H. Self","orcid":"0000-0002-9300-3045","position":25,"is_corresponding":false},{"id":697145,"name":"Influenza and Other Viruses in the Acutely Ill (IVY) Network","orcid":null,"position":26,"is_corresponding":false},{"id":105907,"name":"Carlos G. Grijalva","orcid":"0000-0002-2329-7797","position":0,"is_corresponding":true}],"reference_count":39,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:46:02.603031Z","pmid":"34014274","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}