@fiftiesmum
Not proof of a covid link but perhaps has an effect.
Covid is a viral respiratory disease, there's 20 years of evidence to prove that vit D levels are a key factor in the immune response. The biomed specialists have got the pathway - it's common knowledge in expert circles.
How many more studies would be sufficient ? Blood samples have been taken from covid 19 patients in New Orleans, Indonesia and the Philippines (nearly all severe cases have had massive deficiency, but media don't want to talk about it because vitamin D3 is very, very inexpensive):
medrxiv.org/content/10.1101/2020.04.24.20075838v1
papers.ssrn.com/sol3/papers.cfm?abstract_id=3585561
papers.ssrn.com/sol3/papers.cfm?abstract_id=3571484
dropbox.com/s/ka7h4fbi7xdz9s9/Covid-19%20and%20Vitamin%20D%20Information.pdf?dl=0
onlinelibrary.wiley.com/doi/epdf/10.1111/apt.15777
www.ncbi.nlm.nih.gov/pubmed/30675873
clinmedjournals.org/articles/jide/journal-of-infectious-diseases-and-epidemiology-jide-3-030.php?jid=jide
www.bmj.com/content/368/bmj.m1101/rr-10
www.ncbi.nlm.nih.gov/pmc/articles/PMC5576417/
imj.ie/wp-content/uploads/2020/04/Optimisation-of-Vitamin-D-Status-for-Enhanced-Immuno-protection-Against-Covid-19.pdf
www.ncbi.nlm.nih.gov/pmc/articles/PMC4488782/
thorax.bmj.com/content/70/7/617
Vitamin D deficiency contributes directly to the acute respiratory distress syndrome (ARDS)
www.atsjournals.org/doi/abs/10.1164/ajrccm-conference.2016.193.1_MeetingAbstracts.A1846
Low Vitamin D Status Occurs in 90% of Patients with ARDS and Is Associated with Longer Duration of Mechanical Ventilation