{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T00:58:21Z","timestamp":1788742701462,"version":"build-2803163510"},"reference-count":43,"publisher":"Oxford University Press (OUP)","issue":"6","license":[{"start":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T00:00:00Z","timestamp":1769472000000},"content-version":"vor","delay-in-days":4,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005847","name":"Health and Medical Research Fund","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100005847","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100022720","name":"Health Bureau","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100022720","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100017649","name":"Government of the Hong Kong Special Administrative Region","doi-asserted-by":"publisher","award":["INF-HKU-3"],"award-info":[{"award-number":["INF-HKU-3"]}],"id":[{"id":"10.13039\/501100017649","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001839","name":"University Grants Committee","doi-asserted-by":"publisher","award":["HKU SRFS2021-7S03"],"award-info":[{"award-number":["HKU SRFS2021-7S03"]}],"id":[{"id":"10.13039\/501100001839","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,6,16]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Given concerns that influenza vaccine effectiveness (VE) might differ with repeated annual vaccination, we estimated VE against influenza-associated hospitalization and assessed repeat vaccination effects.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We analyzed a test-negative design study conducted in 3 Hong Kong hospitals (October 2015 - July 2025), excluding the 2020\/21 and 2021\/22 seasons due to the absence of influenza circulation during the COVID-19 pandemic. Polymerase chain reaction testing was used to identify influenza virus infections. We used conditional logistic regression to estimate influenza VE overall, by influenza type\/subtype, and by influenza vaccination status in the preceding year (repeat vaccination status).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>We analyzed data on 34 237 children, among whom 5245 (15.3%) tested positive for influenza. VE against influenza-associated hospitalization was 57.2% (95% confidence interval [CI]: 52.3%, 61.6%), with subtype-specific VE estimates of 67.7% (95% CI: 61.8%, 72.7%) for A(H1N1)pdm09, 60.6% (95% CI: 50.8%, 68.5%) for influenza B, and 37.2% (95% CI: 24.7%, 47.6%) for A(H3N2). The overall \u0394VE (repeated VE \u2212 current only VE) was \u221213.6% (95% CI: \u221233.2%, 3.2%), indicating lower VE among repeatedly vaccinated children.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Current influenza vaccination programs provide substantial protection, but could be further improved by strategies that mitigate repeat vaccination effects, and further research is needed to identify such strategies.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/infdis\/jiag047","type":"journal-article","created":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T12:57:25Z","timestamp":1769086645000},"page":"e1355-e1363","source":"Crossref","is-referenced-by-count":2,"title":["Influenza Vaccination Effectiveness Against Influenza-Associated Hospitalization in Children and the Effects of Repeated Vaccination"],"prefix":"10.1093","volume":"233","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-8840-3029","authenticated-orcid":false,"given":"Xuan","family":"Yu","sequence":"first","affiliation":[{"name":"World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"So-Lun","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mike Y W","family":"Kwan","sequence":"additional","affiliation":[{"name":"Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4374-5921","authenticated-orcid":false,"given":"Shuyi","family":"Zhong","sequence":"additional","affiliation":[{"name":"World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-6570-0582","authenticated-orcid":false,"given":"Caitriona","family":"Murphy","sequence":"additional","affiliation":[{"name":"World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eunice L Y","family":"Chan","sequence":"additional","affiliation":[{"name":"Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joshua S C","family":"Wong","sequence":"additional","affiliation":[{"name":"Department of Paediatrics and Adolescent Medicine, Princess Margaret Hospital , Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0856-0294","authenticated-orcid":false,"given":"Sheena G","family":"Sullivan","sequence":"additional","affiliation":[{"name":"School of Clinical Sciences, Monash University , Melbourne, VIC ,","place":["Australia"]},{"name":"Fielding School of Public Health, University of California, Los Angeles (UCLA) , Los Angeles, California"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Malik","family":"Peiris","sequence":"additional","affiliation":[{"name":"Centre for Immunology & Infection, Hong Kong Science and Technology Park , New Territories, Hong Kong Special Administrative Region ,","place":["China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6297-7154","authenticated-orcid":false,"given":"Benjamin J","family":"Cowling","sequence":"additional","affiliation":[{"name":"World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, The University of Hong Kong , Hong Kong Special Administrative Region 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