Methods
We conducted a review of the evidence relating viral and respiratory
tract infections to vitamin D deficiency. We searched for papers
investigating the effects of vitamin D supplementation on the immune and
inflammatory responses. Finally, we reviewed all articles related to
COVID-19 and registered trials on the use of vitamin D in managing
COVID-19 illness. All relevant entries on MEDLINE and EMBASE databases
up to May 2020 were included in the discussion.