{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:30:26Z","timestamp":1772253026740,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2022,7,2]],"date-time":"2022-07-02T00:00:00Z","timestamp":1656720000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the UC San Diego Office of Research Affairs"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>(1) Background: Vitamin D supplementation has been proposed for the prevention and treatment of COVID-19, but it is not clear if reduced serum vitamin D predisposes individuals to COVID-19 and\/or is a secondary consequence of infection. This study assessed the temporal association between serum vitamin D and COVID-19 with two single-institution case\u2013control studies through the University of California San Diego (UCSD) Health System. (2) Methods: This study included patients who tested positive for COVID-19 from 1 January to 30 September 2020 with serum 25-hydroxy-vitamin D (25(OH)D) measured within 180 days of diagnosis. Patients were separated based on whether 25(OH)D was measured before (n = 107 cases, 214 controls) or after (n = 203 cases, 406 controls) COVID-19 diagnosis. COVID-19 infection status was the outcome variable in the pre-diagnosis study, whereas serum 25(OH)D level was the outcome variable in the post-diagnosis study. (3) Results: Serum 25(OH)D levels were not associated with the odds of subsequent COVID-19 infection (OR 1.0, 95% CI: 1.0 to 1.0, p = 0.98). However, COVID-19-positive individuals had serum 25(OH)D measurements that were 2.7 ng\/mL lower than the controls (95% CI: \u22125.2 to \u22120.2, p = 0.03). (4) Conclusions: In our study population, serum 25(OH)D levels were not associated with the risk of acquiring COVID-19 infection but were reduced in subjects after COVID-19 infection. These results support the possibility that reduced serum 25(OH)D is a consequence and not a cause of COVID-19 infection.<\/jats:p>","DOI":"10.3390\/nu14132757","type":"journal-article","created":{"date-parts":[[2022,7,4]],"date-time":"2022-07-04T20:59:18Z","timestamp":1656968358000},"page":"2757","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Temporal Association of Reduced Serum Vitamin D with COVID-19 Infection: Two Single-Institution Case\u2013Control Studies"],"prefix":"10.3390","volume":"14","author":[{"given":"Diviya","family":"Gupta","sequence":"first","affiliation":[{"name":"School of Medicine, University of California San Diego, La Jolla, CA 92093, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sahit","family":"Menon","sequence":"additional","affiliation":[{"name":"School of Medicine, University of California San Diego, La Jolla, CA 92093, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael H.","family":"Criqui","sequence":"additional","affiliation":[{"name":"School of Medicine, University of California San Diego, La Jolla, CA 92093, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bryan K.","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Medicine, University of California San Diego, La Jolla, CA 92093, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"8251","DOI":"10.3390\/nu7105392","article-title":"Mechanisms Underlying the Regulation of Innate and Adaptive Immunity by Vitamin D","volume":"7","author":"Wei","year":"2015","journal-title":"Nutrients"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1007\/s11882-009-0012-7","article-title":"Vitamin D, Respiratory Infections, and Asthma","volume":"9","author":"Ginde","year":"2009","journal-title":"Curr. 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