Low vitamin D status is associated with coronavirus disease 2019 outcomes: a systematic review and meta-analysis

Int J Infect Dis. 2021 Mar;104:58-64. doi: 10.1016/j.ijid.2020.12.077. Epub 2021 Jan 2.


Background: Observational studies suggest that the risk and clinical prognosis of coronavirus disease 2019 (COVID-19) are related to low vitamin D status; however, the data are inconsistent.

Objectives: We conducted a systematic review and meta-analysis to assess the association between low vitamin D status and COVID-19.

Methods: A systematic search was conducted with PubMed, Embase, and the Cochrane Library from database inception to September 25, 2020. The standardized mean difference (SMD) or odds ratio (OR) and corresponding 95% confidence interval (CI) was applied to estimate pooled results. Random - or fixed-effect models based on heterogeneity were used for the meta-analysis. Funnel plots and Egger regression tests were used to assess publication bias.

Results: A total of ten articles with 361,934 participants were selected for meta-analysis. Overall, the pooled OR in the fixed-effect model showed that vitamin D deficiency or insufficiency was associated with an increased risk of COVID-19 (OR = 1.43, 95% CI 1.00-2.05). In addition, COVID-19-positive individuals had lower vitamin D levels than COVID-19-negative individuals (SMD = -0.37, 95% CI = -0.52 to -0.21). Significant heterogeneity existed in both endpoints. Funnel plots and Egger regression tests revealed significant publication bias.

Conclusions: This systematic review and meta-analysis indicated that low vitamin D status might be associated with an increased risk of COVID-19 infection. Further studies are needed to evaluate the impact of vitamin D supplementation on the clinical severity and prognosis in patients with COVID-19.

Systematic review registration: PROSPERO registration no: CRD42020216740.

Keywords: 25-hydroxyvitamin D; Coronavirus disease 2019; Low vitamin D status; Meta-analysis; Vitamin D.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • COVID-19 / etiology*
  • Dietary Supplements
  • Humans
  • SARS-CoV-2*
  • Vitamin D / administration & dosage
  • Vitamin D Deficiency / complications*


  • Vitamin D