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oai:repisalud.isciii.es:20.500.12105/165512024-11-29T08:12:07Zcom_20.500.12105_2052com_20.500.12105_2051com_20.500.12105_15322col_20.500.12105_19609col_20.500.12105_16968

00925njm 22002777a 4500 dc Martínez-Baz, Iván author Fernández-Huerta, Miguel author Navascués, Ana author Pozo Sanchez, Francisco author Trobajo-Sanmartín, Camino author Casado, Itziar author Echeverria, Aitziber author Ezpeleta, Carmen author Castilla Catalán, Jesús author 2023-09-12 We estimated influenza vaccine effectiveness (IVE) in preventing outpatient and hospitalized cases in the 2022-2023 season. A test-negative design included a representative sample of outpatients and all hospitalized patients with influenza-like illness (ILI) from October 2022 to May 2023 in Navarre, Spain. ILI patients were tested by PCR for influenza virus. Influenza vaccination status was compared between confirmed influenza cases and test-negative controls. Among 3321 ILI patients tested, IVE to prevent influenza cases was 34% (95% confidence interval (CI): 16 to 48) overall, 85% (95%CI: 63 to 94) against influenza B, and 28% (95%CI: 3 to 46) against A(H3N2). Among 558 outpatients, 222 (40%) were confirmed for influenza: 55% A(H3N2), 11% A(H1N1), and 31% B. Overall, IVE to prevent outpatient cases was 48% (95%CI: 8 to 70), 88% (95%CI: 3 to 98) against influenza B, and 50% (95%CI: -4 to 76) against A(H3N2). Of 2763 hospitalized patients, 349 (13%) were positive for influenza: 64% A(H3N2), 17% A(H1N1), and 8% B. IVE to prevent hospitalization was 24% (95%CI: -1 to 42) overall, 82% (95%CI: 49 to 93) against influenza B, and 16% (95%CI: -17 to 40) against A(H3N2). No IVE was observed in preventing influenza A(H1N1). IVE was high to prevent influenza B, moderate against A(H3N2) and null against A(H1N1). A lower proportion of influenza B cases may explain the smaller IVE in hospitalized patients than in outpatients. The null IVE against A(H1N1) was consistent with the observed antigenic drift and supports the new composition of the 2023-2024 influenza vaccine. Vaccines (Basel). 2023 Sep 12;11(9):1478. 10.3390/vaccines11091478 2076-393X Vaccines 37766154 http://hdl.handle.net/20.500.12105/16551 Case-control study Influenza Influenza vaccine Repeated vaccination Vaccine effectiveness Influenza Vaccine Effectiveness in Preventing Laboratory-Confirmed Influenza Cases and Hospitalizations in Navarre, Spain, 2022-2023