Objective: This living systematic review aims to provide a timely, rigorous, and continuously updated summary of the available evidence on the role of vitamin C in treating patients with COVID-19.
Data sources: We conducted searches in PubMed/MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), grey literature, and in a centralized repository in L·OVE (Living OVerview of Evidence). In response to the COVID-19 emergency, L·OVE was adapted to expand the range of evidence it comprises and has been customized to group all COVID-19 evidence in one place. All the searches covered the period until April 29, 2020 (one day before submission).
Study selection and methods: We adapted an already published standard protocol for multiple parallel systematic reviews. We searched for randomized trials evaluating the effect, in patients with COVID-19, of vitamin C versus placebo or no treatment. Anticipating the lack of randomized trials directly addressing this question, we also searched for trials evaluating MERS-CoV and SARS-CoV, and non-randomized studies in COVID-19. Two reviewers independently screened each study for eligibility. A living, web-based version of this review will be openly available during the COVID-19 pandemic, and we will resubmit it to the journal whenever there are substantial updates.
Results: We screened 95 records, but no study was considered eligible. We identified 20 ongoing studies, including 13 randomized trials evaluating vitamin C in COVID-19.
Conclusions: We did not find any studies that met our inclusion criteria, and hence there is no evidence to support or refute the use of vitamin C in the treatment of patients with COVID-19. A substantial number of ongoing studies should provide valuable evidence to inform researchers and decision-makers soon.
Prospero registration number: CRD42020181216.
Keywords: Ascorbic Acid; Coronavirus Infections; Coronavirus disease; Severe Acute Respiratory Syndrome Coronavirus 2; Systematic Review; Vitamin C; COVID-19.