30 Dec '20 16:12>2 edits
@eladar saidYou mean these studies?
I am pretty sure I just answered your question.
Who is going to fund the study you want? All we can have are observational studies because nobody is going to fund a vitamin D covid study, nobody will become a billionaire.
If the study was to be done, big pharm would only miss out on the money.
https://clinicaltrials.gov/ct2/show/NCT04536298
https://clinicaltrials.gov/ct2/show/NCT04579640
https://clinicaltrials.gov/ct2/show/NCT04449718
EDIT: Also there's this one in MedRxiv (not peer reviewed but looks solid)
"This trial does not support the use of vitamin D3 supplementation as an adjuvant treatment of patients with COVID-19."
https://www.medrxiv.org/content/10.1101/2020.11.16.20232397v1
EDIT 2: Your financial argument doesn't make sense. There are 3 large clinical trials ongoing and dozens of research articles. Obviously there's financial backing for it, but the issue appears to be that it doesn't work.