Supplementary material_Vitamin D and COVID-19 systematic review and meta-analysis

The supplementary data file contains the following sections:
1. Search strategy: Search strategy used for the systematic review in databases PubMed, EMBASE, Scopus, Web of Science and Cochrane library.
2. Data extraction sheet - the tool used to extract data from selected research articles
3. Summary of excluded studies - A table of studies that were excluded from the systematic review and meta-analysis after perusing the full-text.
4. Risk of bias of individual studies - risk of bias across five domains in all selected studies, illustrated individually.
5. Statistical analyses for the association between low vitamin D and susceptibility to COVID-19: Outcomes of Funnel plot, Egger's test, sensitivity analysis, subgroup analysis, meta-regression (with model comparisons) conducted with R software for the above association.
6. Comparison of vitamin D levels in people with and without COVID-19: Funnel plot, Egger's test, sensitivity analysis performed using R software.
7. Statistical analyses for the association between low vitamin D and severe COVID-19: similar to section 5.
8. Comparison of vitamin D levels in people with severe and non-severe COVID-19: similar to section 6.
9. Statistical analyses for the association between low vitamin D and death due to COVID-19: similar to section 5.
10. Comparison of vitamin D levels in survivors and non-survivors of COVID-19: similar to section 6.