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

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