{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T20:51:12Z","timestamp":1790455872919,"version":"4.1.0"},"reference-count":39,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2025,6,17]],"date-time":"2025-06-17T00:00:00Z","timestamp":1750118400000},"content-version":"vor","delay-in-days":16,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Influenza Resp Viruses"],"published-print":{"date-parts":[[2025,6]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>The Finnish influenza surveillance system combines traditional virological surveillance and analyses of electronic health records. This paper describes the influenza epidemiology in Finland (population: 5.5 million) during and after the COVID\u201019 pandemic based on national surveillance data from 2019 to 2024.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Influenza incidence was evaluated based on three register\u2010based outcomes: laboratory\u2010confirmed infections, primary health care visits, and hospitalizations. Virus\u2010type distributions were analyzed from respiratory specimens. In register\u2010based analyses, vaccination coverage and vaccine effectiveness were assessed for the two cohorts universally included in the Finnish vaccination program: children aged \u2264\u20096 years and adults aged \u2265\u200965\u2009years.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The 2019\/2020 influenza epidemic ended with the introduction of COVID\u201019 containment measures. In 2020\/2021, influenza was largely absent. The 2021\/2022 epidemic peaked exceptionally late. Influenza activity returned to prepandemic levels in 2022\/2023. None of the 717 sentinel specimens tested positive for B\/Yamagata. Although the percentage of vaccinated young children was constant (31% [100,387\/323,614] to 37% [126,984\/346,344]), the percentage of vaccinated elderly people increased from 48% (577,404\/1,211,732) in 2019\/2020 to 63% (787,771\/1,255,644) in 2021\/2022. The vaccine effectiveness against hospitalization due to laboratory\u2010confirmed influenza in young children and elderly people was 68% (95% confidence interval: 38%; 83%) and 42% (34%; 50%) in 2022\/2023, respectively, and slightly lower in 2023\/2024.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The COVID\u201019 pandemic had two potentially lasting effects on influenza: elimination of the B\/Yamagata lineage and improved vaccination coverage in the elderly population in Finland. To strengthen the Finnish influenza surveillance system, participation in sentinel surveillance must be improved.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/irv.70131","type":"journal-article","created":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T01:23:28Z","timestamp":1750209808000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Influenza Epidemiology in Finland During and After the COVID\u201019 Pandemic: Surveillance Data Analysis (2019\u20132024)"],"prefix":"10.1111","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7456-8016","authenticated-orcid":false,"given":"Ulrike","family":"Baum","sequence":"first","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Niina","family":"Ikonen","sequence":"additional","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oskari","family":"Luomala","sequence":"additional","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5776-5897","authenticated-orcid":false,"given":"Eero","family":"Poukka","sequence":"additional","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"},{"name":"Department of Public Health, Faculty of Medicine University of Helsinki  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tuija","family":"Leino","sequence":"additional","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hanna","family":"Nohynek","sequence":"additional","affiliation":[{"name":"Department of Public Health Finnish Institute for Health and Welfare  Helsinki Finland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2025,6,17]]},"reference":[{"key":"e_1_2_9_2_1","volume-title":"Global Epidemiological Surveillance Standards for Influenza","author":"World Health Organization","year":"2013"},{"key":"e_1_2_9_3_1","unstructured":"THL \u201cInfluenza Surveillance System \u201d Accessed October 28 2024 https:\/\/thl.fi\/en\/topics\/infectious\u2010diseases\u2010and\u2010vaccinations\/surveillance\u2010and\u2010registers\/disease\u2010specific\u2010monitoring\u2010systems\/influenza\u2010surveillance\u2010system."},{"key":"e_1_2_9_4_1","unstructured":"THL \u201cVuosiseurantaraportit influenssasta\u2014THL. 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