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Search strategy.
| Source | Search Strategy | Time Frame |
|---|---|---|
| PubMed | COVID-19 Search String from [153] AND (“vitamin d” or “d3” or “25(OH)D” or “25-hydroxyvitamin D”) | 1 November 2019–27 March 2021 |
| https://c19vitamind.com (accessed on 27 March 2021) | Restriction to category “Levels” | 1 November 2019–27 March 2021 |
