initial publications
https://academic.oup.com/jcem/advance-article/doi/10.1210/clinem/dgaa733/5934827

UK biobank
Our findings do not support a potential link between vitamin D concentrations and risk of COVID-19 infection, nor that vitamin D concentration may explain ethnic differences in COVID-19 infection.
https://pubmed.ncbi.nlm.nih.gov/32413819/

Lancet
https://www.thelancet.com/journals/landia/article/PIIS2213-8587(20)30268-0/fulltext

systematic review on vitamin D supplementation and preventing acute resp infections
BMJ 2017
https://www.bmj.com/content/356/bmj.i6583
Meta-analysis of IPD from 10 933 participants in 25 randomised controlled trials showed an overall protective effect of vitamin D supplementation against acute respiratory tract infection (number needed to treat (NNT)=33)

June 2020

SACN –
https://www.gov.uk/government/news/insufficient-evidence-for-vitamin-d-preventing-or-treating-artis
ie evidence poor quality so more to do with studies not being done rather than the studies having been done and not showing a benefit

NICE said
There is no evidence to support taking vitamin D supplements to specifically prevent or treat COVID-19. However, all people should continue to follow UK Government advice on daily vitamin D supplementation to maintain bone and muscle health during the COVID-19 pandemic. 

5 observational studies on vitamin D and COVID-19 published on or before 18 June 2020. All 5 studies were assessed as being very low quality evidence, at high risk of bias
https://www.nice.org.uk/news/article/nice-phe-and-sacn-publish-rapid-covid-19-guidance-on-vitamin-d

https://www.nutrition.org.uk/healthyliving/covid19/vitamindreviews.html

https://www.nhs.uk/conditions/coronavirus-covid-19/people-at-higher-risk/get-vitamin-d-supplements/

https://www.thelancet.com/journals/landia/article/PIIS2213-8587(20)30268-0/fulltext

covit trial
https://clinicaltrials.gov/ct2/show/NCT04344041
anders

coronavit – big in uK
https://clinicaltrials.gov/ct2/show/NCT04579640

4 nations arranged for shielding patients too get vitamin d either sent out or organised on request

https://www.bbc.co.uk/news/health-55108613

Click to access Shielding-Health-and-Wellbeing-Protection-Levels-Letter-FINAL-231020.pdf

https://www.nhs.uk/conditions/coronavirus-covid-19/people-at-higher-risk/get-vitamin-d-supplements/