Abstract: PLOS ONE RESEARCH ARTICLE Vitamin D sufficiency, a serum 25hydroxyvitamin D at least 30 ng/mL reduced risk for adverse clinical outcomes in patients with COVID-19 infection a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Maghbooli Z, Sahraian MA, Ebrahimi M, Pazoki M, Kafan S, Tabriz HM, et al. (2020) Vitamin D sufficiency, a serum 25-hydroxyvitamin D at least 30 ng/mL reduced risk for adverse clinical outcomes in patients with COVID-19 infection. PLoS ONE 15(9): e0239799. https://doi.org/ 10.1371/journal.pone.0239799 Editor: Muhammad Adrish, BronxCare Health System, Affiliated with Icahn School of Medicine at Mount Sinai, NY, USA, UNITED STATES Received: July 19, 2020 Zhila Maghbooli ID1,2, Mohammad Ali Sahraian1*, Mehdi Ebrahimi3, Marzieh Pazoki4, Samira Kafan5, Hedieh Moradi Tabriz6, Azar Hadadi5, Mahnaz Montazeri5, Mehrad Nasiri2, Arash Shirvani7, Michael F. Holick7* 1 Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran, 2 Research Development Center, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran, 3 Endocrinology Department, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran, 4 Department of Infectious Diseases, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran, 5 Department of Internal Medicine, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran, 6 Department of Pathology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran, 7 Department of Medicine, Section of Endocrinology, Nutrition, Diabetes and Weight Management, Boston University Medical Center, Boston, Massachusetts, United States of America * mfholick@bu.edu (MFH); msahrai@tums.ac.ir (MAS) Abstract Background To investigate the association between serum 25-hydroxyvitamin D levels and its effect on adverse clinical outcomes, and parameters of immune function and mortality due to a SARS-CoV-2 infection. Accepted: September 14, 2020 Published: September 25, 2020 Study design Copyright: © 2020 Maghbooli et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The hospital data of 235 patients infected with COVID-19 were analyzed. Data Availability Statement: The data is part of the inpatient database of Sina Hospital COVID-19 Registry (SHCo-19R) and was used under license for the current study. The datasets used and analyzed during the current study will be available from the Research Development Center of Sina Hospital (Dr. Hale Ashraf; sina.research. development.center@gmail.com) on reasonable request. Based on the ethics board of Tehran University of Medical Sciences, access to data Results Based on CDC criteria, among our study patients, 74% had severe COVID-19 infection and 32.8% were vitamin D sufficient. After adjusting for confounding factors, there was a significant association between vitamin D sufficiency and reduction in clinical severity, inpatient mortality serum levels of C-reactive protein (CRP) and an increase in lymphocyte percentage. Only 9.7% of patients older than 40 years who were vitamin D sufficient succumbed to the infection compared to 20% who had a circulating level of 25(OH)D< 30 ng/ml. The significant reduction in serum CRP, an inflammatory marker, along with increased..