Insufficient evidence for vitamin D use in COVID-19: A rapid systematic review.

Background Vitamin D deficiency has been linked to increased severity of numerous viral infections. Objective To assess whether vitamin D supplementation is safe and effective for the treatment of COVID-19. Methods We searched MEDLINE, EMBASE, CENTRAL, LILACS, and LOVE for randomized controlled trials (RCT) published up to March 2nd evaluating the effects of vitamin D for the treatment of coronavirus disease (COVID-19). Two authors selected studies and analyzed the data evidence following Cochrane Recommendations. Results We included three RCTs with a total of 285 participants. We found low certainty-evidence indicating that hospitalized patients under calcifediol plus standard care (SC) treatment seem to present a significantly lower risk of being admitted to ICU, but no difference on mortality. We found low to very low certainty-evidence that the improvement in fibrinogen levels is slightly greater in mildly symptomatic or asymptomatic patients with COVID-19 that used cholecalciferol plus SC than in those treated with placebo plus SC [Mean difference, and the patients that used cholecalciferol plus SC achieved more SARS-CoV-2 negativity, but not on d-dimer, c-reactive protein (CRP) or procalcitonin when compared with the patients in the placebo plus SC group. We also found low to moderate certainty-evidence that a single high dose of vitamin D does not seem to be effective for reducing mortality, length of hospital stay, ICU admissions, and d-dimer or CRP levels when used in patients with moderate to severe COVID-19. Conclusions As a practical implication, the use of vitamin D associated with SC seems to provide some benefit to patients with COVID-19. However, the evidence is currently insufficient to support the routine use of vitamin D for the management of COVID-19, as its effectiveness seems to depend on the dosage, on the baseline vitamin D levels, and on the degree of COVID-19 severity.