{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T22:37:07Z","timestamp":1790980627211,"version":"4.1.0"},"reference-count":44,"publisher":"Public Library of Science (PLoS)","issue":"12","license":[{"start":{"date-parts":[[2021,12,22]],"date-time":"2021-12-22T00:00:00Z","timestamp":1640131200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005860","name":"Helsefonden","doi-asserted-by":"publisher","award":["17-B-0273"],"award-info":[{"award-number":["17-B-0273"]}],"id":[{"id":"10.13039\/501100005860","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005860","name":"Helsefonden","doi-asserted-by":"publisher","award":["19-B-0352"],"award-info":[{"award-number":["19-B-0352"]}],"id":[{"id":"10.13039\/501100005860","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:sec id=\"sec001\">\n<jats:title>Background<\/jats:title>\n<jats:p>The risk of infectious mononucleosis (IM) is affected both by crowding and by sibship structure, i.e., number and signed age differential between an index child and a sibling. Siblings provide protection against IM by pre-empting delayed primary Epstein-Barr virus infection with its associated high risk of IM. The association between childcare attendance and risk of IM, on the other hand, has never been studied in a large, well-characterized cohort.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec002\">\n<jats:title>Methods<\/jats:title>\n<jats:p>Danish children born in July 1992 through 2016 with a completely known simple childcare attendance history before age 1.5 years (n = 908,866) were followed up for a hospital contact with an IM diagnosis at ages 1.5\u201326 years. Hazard ratios (HRs) of IM for an additional year of exposure were obtained from stratified Cox regression analyses, stratified by sex and year of birth, with age as the underlying time scale, adjusted for sibship structure, and sociodemographic variables including parental ethnicity and maternal age.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec003\">\n<jats:title>Results<\/jats:title>\n<jats:p>An additional year of exclusively attending a daycare home (max 5 children) yielded HR = 0.90 (95% confidence interval 0.81\u20131.00), and similarly, each year of exclusively attending a childcare institution (e.g., cr\u00e8che) yielded HR = 0.94 (0.84\u20131.06).<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec004\">\n<jats:title>Conclusions<\/jats:title>\n<jats:p>Forwarding enrollment in childcare by a year lowers the risk of IM later in life much less than having an additional sibling of comparable age and has no practical public health implications. We find our results suggestive of a random threshold for successful Epstein-Barr virus infection that is more easily reached by a sibling than the collective of playmates in daycare homes or childcare institutions.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pone.0261665","type":"journal-article","created":{"date-parts":[[2021,12,22]],"date-time":"2021-12-22T18:30:06Z","timestamp":1640197806000},"page":"e0261665","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":12,"title":["Childcare attendance and risk of infectious mononucleosis: A population-based Danish cohort study"],"prefix":"10.1371","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6220-9414","authenticated-orcid":true,"given":"Klaus","family":"Rostgaard","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lone Graff","family":"Stensballe","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Signe Holst","family":"S\u00f8egaard","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mads","family":"Kamper-J\u00f8rgensen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Henrik","family":"Hjalgrim","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2021,12,22]]},"reference":[{"key":"pone.0261665.ref001","doi-asserted-by":"crossref","first-page":"1607","DOI":"10.1093\/ije\/dyu118","article-title":"Sibship structure and risk of infectious mononucleosis: a population-based cohort study","volume":"43","author":"K Rostgaard","year":"2014","journal-title":"Int J Epidemiol"},{"key":"pone.0261665.ref002","doi-asserted-by":"crossref","first-page":"e0226436","DOI":"10.1371\/journal.pone.0226436","article-title":"Primary Epstein-Barr virus infection with and without infectious mononucleosis","volume":"14","author":"K Rostgaard","year":"2019","journal-title":"PLoS One"},{"key":"pone.0261665.ref003","doi-asserted-by":"crossref","first-page":"37","DOI":"10.1136\/mp.53.1.37","article-title":"Epstein-Barr virus (EBV) in infectious mononucleosis: detection of the virus in tonsillar B lymphocytes but not in desquamated oropharyngeal epithelial cells","volume":"53","author":"G Niedobitek","year":"2000","journal-title":"Mol Pathol"},{"key":"pone.0261665.ref004","doi-asserted-by":"crossref","first-page":"362","DOI":"10.1089\/vim.2019.0086","article-title":"Subclinical Epstein-Barr Virus Primary Infection and Lytic Reactivation Induce Thyrotropin Receptor Autoantibodies","volume":"32","author":"N Tamoto","year":"2019","journal-title":"Viral Immunol"},{"key":"pone.0261665.ref005","doi-asserted-by":"crossref","first-page":"e1000496","DOI":"10.1371\/journal.ppat.1000496","article-title":"The Dynamics of EBV Shedding Implicate a Central Role for Epithelial Cells in Amplifying Viral Output","volume":"5","author":"V Hadinoto","year":"2009","journal-title":"PLoS Pathog"},{"key":"pone.0261665.ref006","doi-asserted-by":"crossref","first-page":"S52","DOI":"10.1038\/d41586-018-07366-1","article-title":"Building a better lymphoma vaccine","volume":"563","author":"C. 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