Abstract: Accepted Article DR. ALESSANDRO GOROHOVSKI (Orcid ID : 0000-0002-4126-9781) DR. MILANA FRENKEL-MORGENSTERN (Orcid ID : 0000-0002-0329-4599) Received Date : 26-May-2021 Revised Date : 12-Sep-2021 Accepted Date : 04-Oct-2021 Article type : Research Article Seasonal UV exposure and vitamin D: Association with the dynamics of COVID-19 transmission in Europe Sunanda Biswas Mukherjee 1, Alessandro Gorohovski 1, Eugene Merzon 2,3, Eliad Levy 1 Cancer 1, Sumit Mukherjee 1, and Milana Frenkel-Morgenstern 1,* Genomics and BioComputing of Complex Diseases Lab, Azrieli Faculty of Medicine, Bar‐Ilan University, Safed, Israel 2 Leumit Health Services, Tel Aviv, Israel 3 Department of Family Medicine, Sackler School of Medicine, Tel Aviv University, Israel This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2211-5463.13309 FEBS Open Bio (2020) © 2020 The Authors. Published by FEBS Press and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Accepted Article *Correspondence: milana.morgenstern@biu.ac.il Running heading: Association of UV exposure with COVID-19 in Europe Keywords COVID-19; seasonality; ultraviolet (UV) index; cloud-free vitamin D-UV doses (UVDVF); plasma 25(OH) vitamin D Abbreviations DLNM distributed lag non-linear model RR relative risk UV index ultraviolet index UVDVF cloud-free vitamin D-UV doses Abstract Several recent studies have demonstrated that low plasma 25(OH) vitamin D levels are associated with the risk of COVID-19 infection. The primary source of vitamin D production in humans is environmental UV radiation. In many viral respiratory diseases, peak infection rates are observed during winter due to reduced UV exposure and low temperatures. In Europe, the second wave of COVID-19 began early in the winter of 2020. Investigating the impact of seasonal temperature and UV exposure on COVID-19 transmission could thus aid in prevention and intervention. As such, we first performed a comprehensive meta-analysis of all related published literature based on the association of vitamin D and COVID-19, which supported the hypothesis that the low vitamin D level is a critical risk factor for COVID-19 infection. Next, to understand the potential impact of seasonal UV and temperature levels on COVID-19 cases, we analyzed meteorological data and daily COVID19 cases per million in the populations of 26 European countries. We observed that low temperature, FEBS Open Bio (2020) © 2020 The Authors. Published by FEBS Press and John Wiley & Sons Ltd. Accepted Article UV index, and cloud-free vitamin D UV dose (UVDVF) levels are negatively correlated with COVID-19 prevalence in Europe. Furthermore, a distributed lag non-linear model was used to assess the non-linear delayed effects of individual seasonal factors on COVID-19 cases. Such analysis highlighted the significantly delayed impact of UVDVF on the cumulative relative risk of COVID-19 infection. The findings of this study suggest that low UV exposure can affect the required production of vitamin D in the body, which substantially influences the dynamics of COVID-19..