{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T02:46:55Z","timestamp":1772160415839,"version":"3.50.1"},"reference-count":32,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2021,5,4]],"date-time":"2021-05-04T00:00:00Z","timestamp":1620086400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001306","name":"Health Protection Agency","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001306","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Influenza Resp Viruses"],"published-print":{"date-parts":[[2021,9]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>During 2009\u20102010, pandemic influenza A (H1N1) pdm09 virus (pH1N1) infections in England occurred in two epidemic waves. Reasons for a reported increase in case\u2010severity during the second wave are unclear.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We analysed hospital\u2010based surveillance for patients with pH1N1 infections in England during 2009\u20102010 and linked national data sets to estimate ethnicity, socio\u2010economic status and death within 28\u00a0days of admission. We used multivariable logistic regression to assess whether changes in demographic, clinical and management characteristics of patients could explain an increase in ICU admission or death, and accounted for missing values using multiple imputation.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>During the first wave, 54\/960 (6%) hospitalised patients required intensive care and 21\/960 (2%) died; during the second wave 143\/1420 (10%) required intensive care and 55\/1420 (4%) died. In a multivariable model, during the second wave patients were less likely to be from an ethnic minority (OR 0.33, 95% CI 0.26\u20100.42), have an elevated deprivation score (OR 0.75, 95% CI 0.68\u20100.83), have known comorbidity (OR 0.78, 95% CI 0.63\u20100.97) or receive antiviral therapy \u22642\u00a0days before onset (OR 0.72, 95% CI 0.56\u20100.92). Increased case\u2010severity during the second wave was not explained by changes in demographic, clinical or management characteristics.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Monitoring changes in patient characteristics could help target interventions during multiple waves of COVID\u201019 or a future influenza pandemic. To understand and respond to changes in case\u2010severity, surveillance is needed that includes additional factors such as admission thresholds and seasonal coinfections.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/irv.12863","type":"journal-article","created":{"date-parts":[[2021,5,4]],"date-time":"2021-05-04T03:19:23Z","timestamp":1620098363000},"page":"599-607","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Changes in characteristics and case\u2010severity in patients hospitalised with influenza A (H1N1) pdm09 infection between two epidemic waves\u2014England, 2009\u20132010"],"prefix":"10.1111","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4747-381X","authenticated-orcid":false,"given":"Ian D.","family":"Plumb","sequence":"first","affiliation":[{"name":"Public Health England  London UK"},{"name":"London School of Hygiene and Tropical Medicine  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ross","family":"Harris","sequence":"additional","affiliation":[{"name":"Public Health England  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Helen K.","family":"Green","sequence":"additional","affiliation":[{"name":"Public Health England  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Joanna","family":"Ellis","sequence":"additional","affiliation":[{"name":"Public Health England  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kathy","family":"Baisley","sequence":"additional","affiliation":[{"name":"London School of Hygiene and Tropical Medicine  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Richard G.","family":"Pebody","sequence":"additional","affiliation":[{"name":"Public Health England  London UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2021,5,4]]},"reference":[{"key":"e_1_2_10_2_1","doi-asserted-by":"publisher","DOI":"10.1017\/S0950268810002657"},{"key":"e_1_2_10_3_1","unstructured":"McLeanE PebodyR.Epidemiological report of pandemic (H1N1) 2009 in the UK.2010;https:\/\/webarchive.nationalarchives.gov.uk\/20140714113122\/http:\/\/www.hpa.org.uk\/webc\/HPAwebFile\/HPAweb_C\/1284475321350. 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Accessed April 30 2020."},{"key":"e_1_2_10_21_1","article-title":"Inequalities in COVID19 mortality related to ethnicity and socioeconomic deprivation","author":"Rose TC","year":"2020","journal-title":"medRxiv"},{"key":"e_1_2_10_22_1","doi-asserted-by":"publisher","DOI":"10.15585\/mmwr.mm6918e1"},{"key":"e_1_2_10_23_1","doi-asserted-by":"publisher","DOI":"10.3201\/eid1811.120720"},{"key":"e_1_2_10_24_1","doi-asserted-by":"publisher","DOI":"10.3201\/eid1905.130034"},{"key":"e_1_2_10_25_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa0906695"},{"key":"e_1_2_10_26_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pmed.1001053"},{"key":"e_1_2_10_27_1","doi-asserted-by":"crossref","unstructured":"WebbK PeckhamH NdG et al.Sex\u2010bias in COVID\u201019: a meta\u2010analysis and review of sex differences in disease and immunity.2020.https:\/\/www.researchsquare.com\/article\/rs\u201023651\/v2. 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