{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T16:20:56Z","timestamp":1788366056773,"version":"build-2803163510"},"reference-count":38,"publisher":"Oxford University Press (OUP)","issue":"2","license":[{"start":{"date-parts":[[2026,4,12]],"date-time":"2026-04-12T00:00:00Z","timestamp":1775952000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,2]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Immunosuppressed individuals face higher risk of severe influenza complications, yet vaccination coverage remains low. We aimed to assess the effect of electronic letter-based nudges on influenza vaccination uptake by immunosuppression status.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We performed a participant-level pooled analysis of 2 methodologically harmonized, nationwide, pragmatic randomized clinical trials during the 2023\u20132024 influenza season. Adults aged \u226565 years (NUDGE-FLU-2) and adults aged 18\u201364 years with chronic conditions (NUDGE-FLU-CHRONIC) were included, with immunosuppression defined by an immunosuppressive diagnosis or a filled prescription for immunosuppressive therapy. Participants were randomized in a 2.45:1:1:1:1:1:1 ratio to usual care or 1 of 6 electronic letter interventions. The primary outcome was receipt of influenza vaccination by 1 January 2024 ascertained from nationwide administrative health registries. Effect modification by immunosuppression status was assessed using binomial regression.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Among 1 181 254 participants (mean age 67 years; 73 830 [6.3%] immunosuppressed), 66.1% were vaccinated. Any letter increased vaccine uptake compared with usual care (absolute difference, 2.79% points; 95% confidence interval [CI], 2.60\u20132.98; P &amp;lt; .001), with greater effect among immunosuppressed individuals (+4.12 vs +2.70% points; Pinteraction = .002). In younger adults with chronic conditions, letter-based nudges increased vaccination rates by 11.7% points overall and by 13.3% points among those with immunosuppression (Pinteraction = .007). Among immunosuppressed individuals, nudging effects appeared greater for those with immunosuppressive conditions than for those receiving immunosuppressive treatment.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Electronic letter-based nudges increased influenza vaccination rates, with greater benefit among immunosuppressed individuals. These findings support implementation of low-cost, letter-based nudging strategies to improve vaccine uptake in this high-risk population.<\/jats:p>\n                    <jats:p>Clinical Trials Registration. NCT06030726 and NCT06030739.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/cid\/ciag219","type":"journal-article","created":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T11:59:18Z","timestamp":1775649558000},"page":"321-330","source":"Crossref","is-referenced-by-count":0,"title":["Electronic Nudges to Increase Influenza Vaccination in Immunosuppressed Adults Across the Age Spectrum: A Pooled Analysis of 2 Nationwide Randomized Trials"],"prefix":"10.1093","volume":"83","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3272-636X","authenticated-orcid":false,"given":"Anne Marie","family":"Reimer Jensen","sequence":"first","affiliation":[{"name":"Department of Cardiology, Copenhagen University Hospital\u2014Herlev and Gentofte , Copenhagen ,","place":["Denmark"]},{"name":"Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen ,","place":["Denmark"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6959-3236","authenticated-orcid":false,"given":"Niklas Dyrby","family":"Johansen","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Copenhagen University Hospital\u2014Herlev and Gentofte , Copenhagen ,","place":["Denmark"]},{"name":"Center for Translational Cardiology and Pragmatic Randomized Trials, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen ,","place":["Denmark"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-1230-8183","authenticated-orcid":false,"given":"Peter Suldrup","family":"Wolff","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Copenhagen University Hospital\u2014Herlev and Gentofte , Copenhagen ,","place":["Denmark"]},{"name":"Center for Translational Cardiology and Pragmatic Randomized Trials, 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