{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,5]],"date-time":"2026-11-05T12:31:34Z","timestamp":1793881894420,"version":"4.7.0"},"reference-count":34,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T00:00:00Z","timestamp":1777852800000},"content-version":"unspecified","delay-in-days":123,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005416","name":"Norges Forskningsr\u00e5d","doi-asserted-by":"publisher","award":["309762"],"award-info":[{"award-number":["309762"]}],"id":[{"id":"10.13039\/501100005416","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100021078","name":"Norwegian Institute of Public Health","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100021078","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Norwegian Medical Products Agency","id":[{"id":"https:\/\/ror.org\/017gjh659","id-type":"ROR","asserted-by":"crossref"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["Open Heart"],"accepted":{"date-parts":[[2026,4,15]]},"published-print":{"date-parts":[[2026,1]]},"DOI":"10.1136\/openhrt-2026-004112","type":"journal-article","created":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T18:35:16Z","timestamp":1777919716000},"page":"e004112","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Myocarditis after COVID-19 mRNA vaccination in Norway: a nationwide validation study"],"prefix":"10.1136","volume":"13","clinical-trial-number":[{"clinical-trial-number":"nct05610423","registry":"10.18810\/clinical-trials-gov"}],"author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2474-4376","authenticated-orcid":false,"given":"Bendik","family":"Skinningsrud","sequence":"first","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katarina","family":"Vlaisavljevic","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lars Sandve","family":"Oppedal","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Haukeland University Hospital, Bergen, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johannes","family":"Endresen","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Nordland Hospital, Bod\u00f8, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vilde Storesund","family":"Mohn","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Stavanger University Hospital, Stavanger, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristina","family":"Fladseth","sequence":"additional","affiliation":[{"name":"Department of Cardiology, University Hospital of North Norway, Troms\u00f8, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trygve Moe","family":"Lysaker","sequence":"additional","affiliation":[{"name":"Department of Cardiology, St. Olavs Hospital (Trondheim University Hospital), Trondheim, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Margareth Pleym","family":"Ribe","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas Friedrich","family":"M\u00f6ller","sequence":"additional","affiliation":[{"name":"Department of Paediatric Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Torstein Laurits","family":"Hole","sequence":"additional","affiliation":[{"name":"Department of Cardiology, \u00c5lesund Hospital, \u00c5lesund, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesper","family":"Dahl","sequence":"additional","affiliation":[{"name":"Norwegian Institute of Public Health, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u00d8ystein","family":"Karlstad","sequence":"additional","affiliation":[{"name":"Norwegian Institute of Public Health, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hanne L\u00f8vdal","family":"Gulseth","sequence":"additional","affiliation":[{"name":"Norwegian Institute of Public Health, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David Benee","family":"Olsen","sequence":"additional","affiliation":[{"name":"Norwegian Medical Products Agency, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Margrethe","family":"Greve-Isdahl","sequence":"additional","affiliation":[{"name":"Norwegian Institute of Public Health, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sara Viksmoen","family":"Watle","sequence":"additional","affiliation":[{"name":"Norwegian Institute of Public Health, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mette-Elise","family":"Estensen","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kaspar","family":"Broch","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4900-0453","authenticated-orcid":false,"given":"Kristina H","family":"Haugaa","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nina Eide","family":"Hasselberg","sequence":"additional","affiliation":[{"name":"ProCardio Center for Innovation, Department of Cardiology, Oslo University Hospital, Rikshospitalet , Oslo, Norway"},{"name":"Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,5,4]]},"reference":[{"key":"2026110504101080000_13.1.e004112.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMOA2107058"},{"key":"2026110504101080000_13.1.e004112.2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-3946736(21)02183-8"},{"key":"2026110504101080000_13.1.e004112.3","doi-asserted-by":"crossref","first-page":"1668","DOI":"10.1001\/jamainternmed.2021.5511","article-title":"Acute Myocarditis Following COVID-19 mRNA Vaccination in Adults Aged 18 Years or Older","volume":"181","author":"Simone","year":"2021","journal-title":"JAMA Intern Med"},{"key":"2026110504101080000_13.1.e004112.4","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2034577"},{"key":"2026110504101080000_13.1.e004112.5","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2035389"},{"key":"2026110504101080000_13.1.e004112.6","doi-asserted-by":"crossref","first-page":"2132","DOI":"10.1056\/NEJMoa2110737","article-title":"Myocarditis after Covid-19 Vaccination in a Large Health Care Organization","volume":"385","author":"Witberg","year":"2021","journal-title":"N Engl J Med"},{"key":"2026110504101080000_13.1.e004112.7","doi-asserted-by":"crossref","first-page":"2140","DOI":"10.1056\/NEJMoa2109730","article-title":"Myocarditis after BNT162b2 mRNA Vaccine against Covid-19 in Israel","volume":"385","author":"Mevorach","year":"2021","journal-title":"N Engl J Med"},{"key":"2026110504101080000_13.1.e004112.8","doi-asserted-by":"crossref","DOI":"10.1136\/bmj-2021-068665","article-title":"SARS-CoV-2 vaccination and myocarditis or myopericarditis: population based cohort study","volume":"375","author":"Husby","year":"2021","journal-title":"BMJ"},{"key":"2026110504101080000_13.1.e004112.9","doi-asserted-by":"crossref","first-page":"600","DOI":"10.1001\/jamacardio.2022.0583","article-title":"SARS-CoV-2 Vaccination and Myocarditis in a Nordic Cohort Study of 23 Million Residents","volume":"7","author":"Karlstad","year":"2022","journal-title":"JAMA Cardiol"},{"key":"2026110504101080000_13.1.e004112.10","unstructured":"Norwegian Institute of Public Health . Emergency preparedness register for COVID-19. 2025. Available: https:\/\/www.fhi.no\/en\/id\/corona\/coronavirus\/emergency-preparedness-register-for-covid-19\/"},{"key":"2026110504101080000_13.1.e004112.11","doi-asserted-by":"publisher","DOI":"10.1136\/archdischild-2021-323040"},{"key":"2026110504101080000_13.1.e004112.12","unstructured":"Norwegian Directorate of Immigration . National identity number 2025. Available: https:\/\/www.udi.no\/en\/word-definitions\/national-identity-number\/ [Accessed 31 Oct 2025]."},{"key":"2026110504101080000_13.1.e004112.13","doi-asserted-by":"publisher","DOI":"10.1177\/1403494819859737"},{"key":"2026110504101080000_13.1.e004112.14","doi-asserted-by":"crossref","unstructured":"Trogstad L , Ung G , Hagerup-Jenssen M , et al . The Norwegian immunisation register \u2013 SYSVAK. Euro Surveill 2012;17. doi:10.2807\/ese.17.16.20147-en","DOI":"10.2807\/ese.17.16.20147-en"},{"key":"2026110504101080000_13.1.e004112.15","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1093\/ehjci\/jev014","article-title":"Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the American Society of Echocardiography and the European Association of, Cardiovascular Imaging","volume":"16","author":"Lang","year":"2016","journal-title":"Eur Heart J Cardiovasc Imaging"},{"key":"2026110504101080000_13.1.e004112.16","doi-asserted-by":"crossref","first-page":"1499","DOI":"10.1016\/j.vaccine.2021.11.074","article-title":"Myocarditis and pericarditis: Case definition and guidelines for data collection, analysis, and presentation of immunization safety data","volume":"40","author":"Sexson Tejtel","year":"2022","journal-title":"Vaccine (Auckl)"},{"key":"2026110504101080000_13.1.e004112.17","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijcard.2023.131401"},{"key":"2026110504101080000_13.1.e004112.18","doi-asserted-by":"crossref","DOI":"10.1136\/bmjopen-2016-012832","article-title":"Positive predictive value of cardiovascular diagnoses in the Danish National Patient Registry: a validation study","volume":"6","author":"Sundb\u00f8ll","year":"2016","journal-title":"BMJ Open"},{"key":"2026110504101080000_13.1.e004112.19","doi-asserted-by":"crossref","first-page":"410","DOI":"10.1038\/s41591-021-01630-0","article-title":"Risks of myocarditis, pericarditis, and cardiac arrhythmias associated with COVID-19 vaccination or SARS-CoV-2 infection","volume":"28","author":"Patone","year":"2022","journal-title":"Nat Med"},{"key":"2026110504101080000_13.1.e004112.20","doi-asserted-by":"crossref","unstructured":"Fairweather D , Beetler DJ , Musigk N , et al . Sex and gender differences in myocarditis and dilated cardiomyopathy: An update. Front Cardiovasc Med 2023;10. doi:10.3389\/fcvm.2023.1129348","DOI":"10.3389\/fcvm.2023.1129348"},{"key":"2026110504101080000_13.1.e004112.21","doi-asserted-by":"crossref","unstructured":"Le Vu S , Bertrand M , Semenzato L , et al . Influence of mRNA Covid-19 vaccine dosing interval on the risk of myocarditis. Nat Commun 2024;15. doi:10.1038\/s41467-024-52038-6","DOI":"10.1038\/s41467-024-52038-6"},{"key":"2026110504101080000_13.1.e004112.22","doi-asserted-by":"crossref","DOI":"10.1001\/jamanetworkopen.2022.18505","article-title":"Epidemiology of Myocarditis and Pericarditis Following mRNA Vaccination by Vaccine Product, Schedule, and Interdose Interval Among Adolescents and Adults in Ontario, Canada","volume":"5","author":"Buchan","year":"2022","journal-title":"JAMA Netw Open"},{"key":"2026110504101080000_13.1.e004112.23","doi-asserted-by":"publisher","DOI":"10.1016\/j.jacc.2024.10.080"},{"key":"2026110504101080000_13.1.e004112.24","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1002\/clc.23965","article-title":"Development of myocarditis and pericarditis after COVID\u201019 vaccination in children and adolescents: A systematic review","volume":"46","author":"Fatima","year":"2023","journal-title":"Clin Cardiol"},{"key":"2026110504101080000_13.1.e004112.25","doi-asserted-by":"publisher","DOI":"10.1001\/jama.2021.24110"},{"key":"2026110504101080000_13.1.e004112.26","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1016\/j.ijid.2023.03.004","article-title":"Effectiveness of BNT162b2 vaccine against SARS-CoV-2 Delta and Omicron infection in adolescents","volume":"130","author":"Veneti","year":"2021","journal-title":"Int J Infect Dis"},{"key":"2026110504101080000_13.1.e004112.27","unstructured":"Norwegian Institute of Public Health . Svar p\u00e5 oppdrag 58 \u2013 om dose to til 12-15 \u00e5ringer. 2022. Available: https:\/\/www.fhi.no\/contentassets\/3596efb4a1064c9f9c7c9e3f68ec481f\/2022-01-07-svar-pa-oppdrag-58-om-dose-to-til-12-15-aringer.pdf"},{"key":"2026110504101080000_13.1.e004112.28","doi-asserted-by":"publisher","DOI":"10.1002\/ejhf.2669"},{"key":"2026110504101080000_13.1.e004112.29","doi-asserted-by":"crossref","first-page":"2255","DOI":"10.1016\/j.jacc.2022.09.049","article-title":"Prognosis of Myocarditis Developing After mRNA COVID-19 Vaccination Compared With Viral Myocarditis","volume":"80","author":"Lai","year":"2022","journal-title":"J Am Coll Cardiol"},{"key":"2026110504101080000_13.1.e004112.30","doi-asserted-by":"publisher","DOI":"10.1093\/eurheartj\/ehad339"},{"key":"2026110504101080000_13.1.e004112.31","doi-asserted-by":"crossref","first-page":"1367","DOI":"10.1001\/jama.2024.16380","article-title":"Long-Term Prognosis of Patients With Myocarditis Attributed to COVID-19 mRNA Vaccination, SARS-CoV-2 Infection, or Conventional Etiologies","volume":"332","author":"Semenzato","year":"2024","journal-title":"JAMA"},{"key":"2026110504101080000_13.1.e004112.32","doi-asserted-by":"crossref","first-page":"E1037","DOI":"10.1161\/CIR.0000000000001064","article-title":"SARS-CoV-2 Infection and Associated Cardiovascular Manifestations and Complications in Children and Young Adults: A Scientific Statement From the American Heart Association","volume":"145","author":"Jone","year":"2022","journal-title":"Circulation"},{"key":"2026110504101080000_13.1.e004112.33","doi-asserted-by":"crossref","first-page":"1536","DOI":"10.1016\/j.cjca.2024.03.016","article-title":"Myocarditis and Pericarditis After mRNA COVID-19 Vaccination: 2024 Status and Management Update","volume":"40","author":"McDonald","year":"2024","journal-title":"Canadian Journal of Cardiology"},{"key":"2026110504101080000_13.1.e004112.34","doi-asserted-by":"crossref","first-page":"136","DOI":"10.1016\/j.ijcard.2022.04.024","article-title":"Temporal relationship of myocarditis and pericarditis following COVID-19 vaccination: A pragmatic approach","volume":"358","author":"Anastassopoulou","year":"2022","journal-title":"Int J Cardiol"}],"container-title":["Open Heart"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/openhrt-2026-004112","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,11,5]],"date-time":"2026-11-05T12:10:22Z","timestamp":1793880622000},"score":1,"resource":{"primary":{"URL":"https:\/\/openheart.bmj.com\/lookup\/doi\/10.1136\/openhrt-2026-004112"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1]]},"references-count":34,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,5,4]]},"published-print":{"date-parts":[[2026,1]]}},"alternative-id":["10.1136\/openhrt-2026-004112"],"URL":"https:\/\/doi.org\/10.1136\/openhrt-2026-004112","relation":{},"ISSN":["2053-3624"],"issn-type":[{"value":"2053-3624","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1]]}}}