The COVID-19 Pandemic, Seasons and the Vitamin D Laboratory Strategy


  • Professor Joško Osredkar


Vitamin D, cholecalciferol, 25-OH-D3, COVID-19, pandemic, SARS-CoV-2, seasons, summer, morbidity, mortality


From the very beginning of the COVID-19 pandemic, the laboratory blood tests and markers are searched as a potential diagnostic tool for this disease and for disease severity assessment. Also from the beginning of the pandemic scientists published reports on the potentially important role of vitamin D on the course of the COVID-19 patients. According to the data there are seasonal fluctuations of COVID-19 severity, where the numbers of newly infected in summertime in contrast to wintertime, are the same or even higher, but there are much less death cases. The different seasonal incidence of infectious diseases has been well known since the Hippocratic period. Vitamin D is a molecule with potent immunomodulatory actions. The effectiveness against various upper respiratory infections is confirmed. Based on the findings of previous research on meta-analysis of interventional studies with vitamin D in respiratory viral infections, based on new COVID-19 observational studies and based on pilot randomized study where vitamin D in COVID-19 patients significantly reduced morbidity and alleviated the course of infection, we emphasize the importance of inclusion of vitamin D routine measurement, before vitamin D treatment in COVID patients becomes a routine. Vitamin D has a small chance of side effects in doses of prevention and therapy. Randomized double blinded clinical trials are needed to finally prove the benefit of supplementation of vitamin D in COVID-19 patients. Until then however, in the COVID pandemic, it is highly ethical to consider and use the current knowledge about the benefits of vitamin D substitution in patients with vitamin D deficiency or insufficiency


. Velavan TP, Meyer CG, Mild versus severe COVID-19: Laboratory markers, International Jofurnal of Infectious Diseases, Volume 95, June 2020, Pages 304-307.

. Zhang J-j, Dong X, Cao Y-y, Yuan Y-d, Yang Y-b, Yan Y-q, et al. Clinical characteristics of 140 patients infected with SARS-CoV-

in Wuhan, China. Allergy. 2020 2020/02/19;n/a(n/a).

. Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. The Lancet (London, England). 2020.

. Liu Y, Yang Y, Zhang C, Huang F, Wang F, Yuan J, et al. Clinical and biochemical indexes from 2019-nCoV infected patients linked to viral loads and lung injury. Science China Life Sciences. 2020 2020/03/01;63(3):364-74

. Brandon Michael H, Maria Helena Santos de O, Stefanie B, Mario P, Giuseppe L. Hematologic, biochemical and immune

biomarker abnormalities associated with severe illness and mortality in coronavirus disease 2019 (COVID-19): a metaanalysis. Clin Chem Lab Med. 2020(0):20200369

. Siuka, D., Pfeifer, M., & Pinter, B. (2020). Vitamin D Supplementation During the COVID-19 Pandemic. Mayo Clinic proceedings, 95(8), 1804–1805.

. Benskin LL, A Basic Review of the Preliminary. Evidence That COVID-19 Risk and Severity Is Increased in Vitamin D Deficiency, Perspective, published: 10 September 2020, doi: 10.3389/fpubh.2020.00513

. Merzon E, Tworowski D, Gorohovski A, Vinker S, Golan Cohen A, Green I, Frenkel-Morgenstern M. Low plasma 25(OH) vitamin D level is associated with increased risk of COVID-19 infection: an Israeli population-based study. FEBS J. 2020 Jul 23:10.1111/febs.15495. doi: 10.1111/febs.15495. Epub ahead of print. PMID: 32700398; PMCID: PMC7404739

. Entrenas Castillo M, Entrenas Costa LM, Vaquero Barrios JM, et al. "Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study" [published online ahead of print, 2020 Aug 29]. J Steroid Biochem Mol Biol. 2020;203:105751. doi:10.1016/j.jsbmb.2020.105751

. Bikle D, Bouillon R, Thadhani R, Schoenmakers I. Vitamin D metabolites in captivity? Should we measure free or total 25(OH)D to assess vitamin D status? J Steroid Biochem Mol Biol. 2017 Oct;173:105-116. doi: 10.1016/j.jsbmb.2017.01.007. Epub 2017 Jan 16. PMID: 28093353.

. Mohan M, Cherian JJ, Sharma A. Exploring links between vitamin D deficiency and COVID-19. PLoS Pathog. 2020 Sep 18;16(9):e1008874. doi: 10.1371/journal.ppat.1008874. PMID: 32946517.

. Worldometer COVID-19 Coronavirus Pandemic (accessed 17 July 2020).

. Liu PT, Stenger S, Li H 14 et al.: Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response. Science 311, 1770–1773 (2006)

. Armas AG l. Vitamin D, infections and immune-mediated diseases. Int.J.Clin.Reumatol.2009; 4(1):89-103. doi: 10.2217/17584272.4.1.89

. Heaney RP, Dowell MS, Hale CA, Bendich 4 A: Calcium absorptirron varies within the reference range for serum 25-hydroxyvitamin D. J. Am. Coll. Nutr. 22, 142 –146 (20 03 )

. Fares A. Factors influencing the seasonal patterns of infectious diseases. Int J Prev Med. 2013;4(2):128-132.

. Grant WB, Giovannucci E. The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918-1919 influenza pandemic in the United States. Dermatoendocrinol. 2009;1(4):215-219. doi:10.4161/derm.1.4.9063

. Aranow C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881-886. doi:10.2310/JIM.0b013e31821b8755

. Dancer RC, Parekh D, Lax S, et al. Vitamin D deficiency contributes directly to the acute respiratory distress syndrome (ARDS). Thorax. 2015;70(7):617-624. doi:10.1136/thoraxjnl-2014-206680

. Zheng Z, M.D. et al, Risk factors of critical & mortal COVID-19 cases: A systematic literature review and meta-analysisJ Infect. 2020 Apr 23. doi: 10.1016/j.jinf.2020.04.021

. Kara M, Ekiz T, Ricci V, Kara Ö, Chang KV, Özçakar L. 'Scientific Strabismus' or two related pandemics: coronavirus disease and vitamin D deficiency [published online ahead of print, 2020 May 12]. Br J Nutr. 2020;1-6. doi:10.1017/S0007114520001749

. Annweiler C, Hanotte B, de l'Eprevier CG, Sabatier JM, Lafaie L, Célarier T. Vitamin D and survival in COVID-19 patients: A quasi-experimental study. J Steroid Biochem Mol Biol. 2020 Oct 13:105771. doi: 10.1016/j.jsbmb.2020.105771. Epub ahead of print. PMID: 33065275; PMCID: PMC7553119. Marcinowska-Suchowierska E, Kupisz-Urbańska M, Łukaszkiewicz J, Płudowski P, Jones G. Vitamin D Toxicity-A Clinical Perspective. Front Endocrinol (Lausanne). 2018;9:550. Published 2018 Sep 20. doi:10.3389/fendo.2018.00550

. Davies G, Garami AR, Byers J. Evidence Supports a Causal Role for Vitamin D Status in Global COVID-19 Outcome. medRxiv preprint:

. Radujkovic A, Hippchen T, Tiwari-Heckler S, Dreher S, Boxberger M, Merle U. Vitamin D Deficiency and Outcome of COVID-19 Patients. Nutrients 2020, 12, 2757; doi:10.3390/nu12092757

. Baktash V, Hosack T, Patel N, et al. Postgrad Med J Epub ahead of print: doi:10.1136/ postgradmedj-2020- 138712

. Meltzer O D, Best J T, Zhang H, Vokes T, Arora V, Solway J. Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results. JAMA Network Open. 2020;3(9):e2019722. doi:10.1001/jamanetworkopen.2020.19722

. Sassi F, Tamone C, D’Amelio P. Vitamin D: nutrient, hormone, and immunomodulator. Nutrients. 2018;10 (11):1656. doi:10.3390/nu10111656

. Greger JL. Effect of Variations in Dietary Protein, Phosphorus, Electrolytes and Vitamin D on Calcium and Zinc Metabolism: Nutrient Interactions. Marcel Dekker; 1988:205-228

. Velthuis AJ, van den Worm SH, Sims AC, Baric RS, Snijder EJ, van Hemert MJ. Zn(2+) inhibits coronavirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture. PLoS Pathog. 2010;6(11):e1001176. doi:10.1371/journal.ppat.1001176




How to Cite

Osredkar, P. J. . (2021). The COVID-19 Pandemic, Seasons and the Vitamin D Laboratory Strategy. International Journal of Sciences: Basic and Applied Research (IJSBAR), 56(2), 182–189. Retrieved from