Vitamin D deficiency and the need to replenish it in COVID-19

More than five years have passed since the beginning of the COVID-19 pandemic, but although the fundamental role of vitamin D’s effect on the immune system is quite obvious to the vast majority of specialists, there are publications expressing a sharply negative attitude towards the use of vitamin D preparations for the treatment of patients infected with SARSCoV- 2. The purpose of the work: «generalization of international experience on the issue of vitamin D deficiency in COVID-19 patients and the need to replenish it.» From the archive of the National Library of Medicine of the USA, containing 15,768 full versions of articles on the effect of vitamin D on the incidence of coronavirus in the population, we selected 49 articles presenting the results of clinical use of vitamin D preparations for the treatment of patients with a confirmed diagnosis of COVID-19. Of these, the results of 38 studies involving more than 3,800 patients infected with SARS-CoV-2 showed positive results of using vitamin D preparations as a therapeutic agent for the treatment of patients with a confirmed diagnosis of COVID-19 (improvement of inflammation markers, reduction of the need for artificial ventilation, reduction of the length of stay in the clinic, reduction of hospital mortality). In three more articles, the authors conclude that the use of vitamin D preparations for the treatment of patients with COVID-19 is ineffective, but they contain information about the usefulness of such use, although the differences in results in the intervention groups and control groups are not statistically significant. Seven articles indicate zero results from the use of vitamin D preparations, and one article says that taking vitamin D worsened the condition of critically ill patients. The ratio of positive, positive, but statistically insignificant, zero and negative results of clinical trials of vitamin D preparations for the treatment of patients with a confirmed diagnosis of COVID-19 (38:3:7:1) It is significantly biased towards the usefulness of vitamin D supplements to reduce the severity of the disease and reduce hospital mortality from coronavirus infection. The most common type of vitamin D drug used in COVID-19 therapy is cholecalciferol, calcidiol is less often used, and calcitriol and ergocalciferol are used even less often (isolated cases have been described). To date, calcidiol has demonstrated the greatest effectiveness in the complex therapy of COVID -19.