{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,21]],"date-time":"2026-08-21T13:46:36Z","timestamp":1787319996797,"version":"build-2736575974"},"reference-count":38,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2024,9,15]],"date-time":"2024-09-15T00:00:00Z","timestamp":1726358400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Immunity debt for various viral infections was reported globally in the post-COVID-19 era, but the data about influenza are lacking. This study collected data from Taiwan\u2019s CDC Open Data Portal. We analyzed the weekly number of influenza hospitalizations from January 2017 to May 2024. We divided the study period into four phases: the pre-COVID-19 without influenza epidemics, pre-COVID-19 with an influenza epidemic, COVID-19 pandemic lockdown control, and COVID-19 pandemic unlock periods. The Wilcoxon rank-sum test and interrupted time series analysis were used. The median case numbers of the four time periods were 174 (IQR = 98), 431 (IQR = 160), 8, and 155 (IQR = 175), respectively. Under the COVID-19 pandemic lockdown control, the weekly influenza hospitalization case number decreased by 90.2% (p &lt; 0.001). The non-pharmaceutical intervention (NPI) policies during the COVID-19 pandemic helped Taiwan reduce influenza hospitalizations significantly. Till now, a comparison of the prevalence of influenza pre-COVID-19 and post-COVID-19 has yet to be reported. In our study, with the pandemic unlocking, it increased by 20-fold (p &lt; 0.001), but the case number was still significantly lower than that pre-COVID-19. Amongst other factors, this may be associated with continuing self-induced NPIs in Taiwan.<\/jats:p>","DOI":"10.3390\/v16091468","type":"journal-article","created":{"date-parts":[[2024,9,16]],"date-time":"2024-09-16T04:14:07Z","timestamp":1726460047000},"page":"1468","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Immunity Debt Regarding the Aspect of Influenza in the Post-COVID-19 Era in Taiwan"],"prefix":"10.3390","volume":"16","author":[{"given":"Edward","family":"Wu","sequence":"first","affiliation":[{"name":"Morrison Academy, Taichung 406, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Victoria","family":"Wu","sequence":"additional","affiliation":[{"name":"Morrison Academy, Taichung 406, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kang-Hsi","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Chung Shan Medical University Hospital, Taichung 402, Taiwan"},{"name":"School of Medicine, Chung Shan Medical University, Taichung 402, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kun-Chan","family":"Wu","sequence":"additional","affiliation":[{"name":"Wu Kun Chan Clinic, Miaoli 360, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0794-9388","authenticated-orcid":false,"given":"Jing-Yang","family":"Huang","sequence":"additional","affiliation":[{"name":"Institute of Medicine, College of Medicine, Chung Shan Medical University, Taichung 402, Taiwan"},{"name":"Department of Medical Research, Chung Shan Medical University Hospital, Taichung 402, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,9,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Yang, M.C., Su, Y.T., Chen, P.H., Tsai, C.C., Lin, T.I., and Wu, J.R. (2023). Changing patterns of infectious diseases in children during the COVID-19 pandemic. Front. Cell Infect. Microbiol., 13.","DOI":"10.3389\/fcimb.2023.1200617"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Terliesner, N., Unterwalder, N., Edelmann, A., Corman, V., Knaust, A., Rosenfeld, L., Gratopp, A., Ringe, H., Martin, L., and von Bernuth, H. (2022). Viral infections in hospitalized children in Germany during the COVID-19 pandemic: Association with non-pharmaceutical interventions. Front. Pediatr., 10.","DOI":"10.3389\/fped.2022.935483"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3249","DOI":"10.1038\/s41467-021-23440-1","article-title":"Impact of COVID-19 outbreaks and interventions on influenza in China and the United States","volume":"12","author":"Feng","year":"2021","journal-title":"Nat. Commun."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1013","DOI":"10.15585\/mmwr.mm7029a1","article-title":"Changes in Influenza and Other Respiratory Virus Activity During the COVID-19 Pandemic\u2014United States, 2020\u20132021","volume":"70","author":"Olsen","year":"2021","journal-title":"MMWR Morb. Mortal. Wkly. Rep."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e2254909","DOI":"10.1001\/jamanetworkopen.2022.54909","article-title":"Circulation of Rhinoviruses and\/or Enteroviruses in Pediatric Patients With Acute Respiratory Illness Before and During the COVID-19 Pandemic in the US","volume":"6","author":"Rankin","year":"2023","journal-title":"JAMA Netw. Open"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"804","DOI":"10.1111\/irv.12884","article-title":"The impact of the 2009 influenza pandemic on the seasonality of human respiratory syncytial virus: A systematic analysis","volume":"15","author":"Li","year":"2021","journal-title":"Influenza Other Respir. Viruses"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"291","DOI":"10.1007\/s00705-023-05891-7","article-title":"The changing pattern of common respiratory viruses among children from 2018 to 2021 in Wuhan, China","volume":"168","author":"Wan","year":"2023","journal-title":"Arch. Virol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1016\/j.puhe.2023.12.009","article-title":"Postpandemic immunity debt of influenza in the USA and England: An interrupted time series study","volume":"227","author":"Leung","year":"2024","journal-title":"Public Health"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"104834","DOI":"10.1016\/j.idnow.2023.104834","article-title":"The outbreak of seasonal influenza after the COVID-19 pandemic in China: Unraveling the \u201cImmunity debt\u201d","volume":"54","author":"Pan","year":"2024","journal-title":"Infect. Dis. Now."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Hu, W., Fries, A.C., DeMarcus, L.S., Thervil, J.W., Kwaah, B., Brown, K.N., Sjoberg, P.A., and Robbins, A.S. (2022). Circulating Trends of Influenza and Other Seasonal Respiratory Viruses among the US Department of Defense Personnel in the United States: Impact of the COVID-19 Pandemic. Int. J. Environ. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph19105942"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"e44","DOI":"10.1016\/S2352-4642(21)00333-3","article-title":"Respiratory syncytial virus: Paying the immunity debt with interest","volume":"5","author":"Hatter","year":"2021","journal-title":"Lancet Child. Adolesc. Health"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.jinf.2023.10.019","article-title":"Exploring immunity debt: Dynamic alterations in RSV antibody levels in children under 5 years during the COVID-19 pandemic","volume":"88","author":"Jiang","year":"2024","journal-title":"J. Infect."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1","DOI":"10.12968\/hmed.2022.0349","article-title":"Immunity debt and unseasonal childhood respiratory viruses","volume":"83","author":"Munro","year":"2022","journal-title":"Br. J. Hosp. Med."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"499","DOI":"10.5582\/bst.2023.01303","article-title":"Immunity debt: Hospitals need to be prepared in advance for multiple respiratory diseases that tend to co-occur","volume":"17","author":"Li","year":"2024","journal-title":"Biosci. Trends"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"223","DOI":"10.1016\/j.jgar.2022.01.010","article-title":"Back to the future (of common respiratory viruses)","volume":"28","author":"Mattana","year":"2022","journal-title":"J. Glob. Antimicrob. Resist."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Methi, F., St\u00f8rdal, K., Telle, K., Larsen, V.B., and Magnusson, K. (2022). Hospital Admissions for Respiratory Tract Infections in Children Aged 0\u20135 Years for 2017\/2023. Front. Pediatr., 9.","DOI":"10.3389\/fped.2021.822985"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"113491","DOI":"10.1016\/j.jpeds.2023.113491","article-title":"Respiratory Syncytial Virus, Influenza, and Coronavirus Disease 2019 Hospitalizations in Children in Colorado During the 2021\u20132022 Respiratory Virus Season","volume":"260","author":"Rao","year":"2023","journal-title":"J. Pediatr."},{"key":"ref_18","first-page":"1","article-title":"How Taiwan Succeeded in Containing Its 2021 COVID-19 Outbreak","volume":"18","author":"Wu","year":"2022","journal-title":"Asian Soc. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"16","DOI":"10.5539\/ass.v16n10p16","article-title":"Response to the Coronavirus Disease-2019 Pandemic: Lessons Learned from the Taiwan Model","volume":"16","author":"Wu","year":"2020","journal-title":"Asian Soc. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Huang, Y.B., Lin, Y.R., Hung, S.K., Chang, Y.C., Ng, C.J., and Chen, S.Y. (2022). Pediatric Training Crisis of Emergency Medicine Residency during the COVID-19 Pandemic. Children, 9.","DOI":"10.3390\/children9010032"},{"key":"ref_21","unstructured":"(2024, September 09). Total COVID-19 Vaccine Doses Administered. Available online: https:\/\/ourworldindata.org\/grapher\/cumulative-covid-vaccinations?tab=chart&country=~TWN."},{"key":"ref_22","unstructured":"(2024, July 20). Timeline of Key Decisions for COVID-19 Epidemic Prevention, Available online: https:\/\/covid19.mohw.gov.tw\/ch\/sp-timeline0-205.html."},{"key":"ref_23","unstructured":"(2024, July 20). Infectious Disease Statistics, Available online: https:\/\/nidss.cdc.gov.tw\/Home\/Index?op=2."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"pgad152","DOI":"10.1093\/pnasnexus\/pgad152","article-title":"Quantifying the rebound of influenza epidemics after the adjustment of zero-COVID policy in China","volume":"2","author":"Lei","year":"2023","journal-title":"PNAS Nexus"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Miron, V.D., Bar, G., Filimon, C., and Craiu, M. (2022). From COVID-19 to Influenza-Real-Life Clinical Practice in a Pediatric Hospital. Diagnostics, 12.","DOI":"10.3390\/diagnostics12051208"},{"key":"ref_26","unstructured":"(2024, September 09). Hospitalization Surveillance, Available online: https:\/\/www.cdc.gov\/flu\/weekly\/index.htm?fbclid=IwY2xjawFKpl9leHRuA2FlbQIxMAABHSh91g_QKnMuBYKT2PTDPBUDm0GD2IcRZRUw_v3gnokf96Exxx3k-yEChw_aem_gBRK5-ENB7x6mbBw7Go2rg#FluSurvNet."},{"key":"ref_27","unstructured":"(2024, September 09). National Healthcare Safety Network (NHSN) Hospitalization Surveillance, Available online: https:\/\/gis.cdc.gov\/grasp\/fluview\/FluView12.html?fbclid=IwY2xjawFKpxxleHRuA2FlbQIxMAABHSa6xzkPLE_YUJLi_P0aE8dqqCjRIKvaJP_WXTAT5sQM3atz_AKMlW_NFA_aem_HIPZV1USpLLxkJN50iq4dg."},{"key":"ref_28","unstructured":"(2024, September 09). Respiratory Virus Hospitalization Surveillance Network (RESP-NET), Available online: https:\/\/www.cdc.gov\/resp-net\/dashboard\/index.html?fbclid=IwY2xjawFKp-pleHRuA2FlbQIxMAABHYUOwRCQ-y8ldIcKg2kDZE-BcSqSVfxBBp-FqJB6fvKNXeTCXWbrEQTibg_aem_6nOLrVFidf0HqpRGld1Gig."},{"key":"ref_29","unstructured":"(2024, September 09). National Influenza and COVID-19 Surveillance Report, Available online: https:\/\/assets.publishing.service.gov.uk\/media\/6620e6d077a30aa0c4757d87\/Weekly_flu_and_COVID-19_report_w16.pdf?fbclid=IwY2xjawFKqR1leHRuA2FlbQIxMAABHeG2p6l_cFZBTUU4GxIImGgYIbKo9G6RUgGWzjUVV_CIcvlWOPk0Tii73Q_aem_iNiN9wIYvAEP8F4Advfl0w."},{"key":"ref_30","unstructured":"(2024, September 09). WHO COVID-19 Dashboard. Available online: https:\/\/data.who.int\/dashboards\/covid19\/cases?n=c."},{"key":"ref_31","unstructured":"(2024, July 20). Flunet. Available online: https:\/\/www.who.int\/tools\/flunet."},{"key":"ref_32","unstructured":"(2024, July 20). Communicable Disease Prevention Information, Available online: https:\/\/data.cdc.gov.tw\/en\/."},{"key":"ref_33","unstructured":"(2024, July 20). Health Insurance Outpatient and Emergency Visits\u2014Influenza, Available online: https:\/\/data.cdc.gov.tw\/en\/dataset\/hi-outpatient-emergency-visit-influenza."},{"key":"ref_34","unstructured":"(2024, July 20). Universal Health Insurance, Available online: https:\/\/www.ey.gov.tw\/state\/A01F61B9E9A9758D\/fa06e0d2-413f-401e-b694-20c2db86f404."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"546","DOI":"10.1111\/j.1750-2659.2012.00422.x","article-title":"Influenza surveillance in Europe: Establishing epidemic thresholds by the moving epidemic method","volume":"7","author":"Vega","year":"2013","journal-title":"Influenza Other Respir. Viruses"},{"key":"ref_36","unstructured":"Caswell, J. (2024, July 20). Lead Analyst. Interrupted Time Series Analysis for Single Series and Comparative Designs: Using Administrative Data for Healthcare Impact Assessment. Available online: https:\/\/www.sas.com\/content\/dam\/SAS\/en_ca\/User%20Group%20Presentations\/Health-User-Groups\/ITS_SAS.pdf."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"104638","DOI":"10.1016\/j.idnow.2022.12.003","article-title":"Immune debt: Recrudescence of disease and confirmation of a contested concept","volume":"53","author":"Cohen","year":"2023","journal-title":"Infect. Dis. Now."},{"key":"ref_38","unstructured":"(2024, July 20). Annual Influenza Vaccination Planning, Available online: https:\/\/www.cdc.gov.tw\/Category\/MPage\/JNTC9qza3F_rgt9sRHqV2Q."}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/16\/9\/1468\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T15:56:48Z","timestamp":1760111808000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/16\/9\/1468"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,9,15]]},"references-count":38,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2024,9]]}},"alternative-id":["v16091468"],"URL":"https:\/\/doi.org\/10.3390\/v16091468","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,9,15]]}}}