Strategic COVID-19 Pandemic Committee 

Does taking Vitamin D daily protect against
COVID-19?

COVID-19 Questions & Myths

There are ongoing studies but, so far, no good quality scientific evidence suggests that Vitamin D either prevents or is useful in treating COVID-19 infection. Some studies have suggested it is useful but others have not. People with Vitamin D deficiency may be more likely to have severe COVID-19, although it is possible that both the Vitamin D deficiency and COVID-19 could be related to other health issues. 

In any case, most Canadians should consider taking Vitamin D supplements in the winter because of low levels due to reduced sunlight exposure (Health Canada guidelines suggest 400-800 iu/d for most people).  

References:
i. Level on Hospital Admission Associated With COVID-19 Stage and Mortality, De Smet D et al. Serum, American Journal of Clinical Pathology  
ii. Vitamin D for COVID-19, National Institute for Health and Care Excellence
iii. Vitamin D and Calcium: Updated Dietary Reference Intakes, Health Canada