Resumen: Vitamin D has an immune-modulating effect on respiratory tract infections. For this reason, it has been proposed as part of the treatment in COVID-19. Furthermore, vitamin D deficiency has been associated with worse clinical outcomes of this disease. The aim of this systematic review was to determine whether vitamin D supplementation modifies the disease course. Therefore, eleven studies involving randomised clinical trials are analysed, in which groups of COVID-19 patients with or without vitamin D supplementation as part of the treatment are compared. A control group was treated with best available therapy, and in some of the clinical trials, also with a placebo. According to the outcomes, it seems that patients benefit from receiving a daily or maintained in time vitamin D dose regardless of vitamin D serum levels at the beginning of the trial. The administration of a single vitamin D dose does not seem to have any effect on the health status of these patients. However, the outcomes are heterogeneous and larger clinical trials are necessary. Idioma: Inglés DOI: 10.3390/ijms232012424 Año: 2022 Publicado en: International Journal of Molecular Sciences 23, 20 (2022), 12424 [15 pp.] ISSN: 1661-6596 Factor impacto JCR: 5.6 (2022) Categ. JCR: BIOCHEMISTRY & MOLECULAR BIOLOGY rank: 66 / 285 = 0.232 (2022) - Q1 - T1 Categ. JCR: CHEMISTRY, MULTIDISCIPLINARY rank: 52 / 178 = 0.292 (2022) - Q2 - T1 Factor impacto CITESCORE: 7.8 - Biochemistry, Genetics and Molecular Biology (Q1) - Computer Science (Q1) - Chemistry (Q1) - Chemical Engineering (Q1) - Medicine (Q1)