Vitamin D and Covid-19?

National Institutes of Health (NIH) peer reviewed journal articles that investigate this matter:

Association between vitamin D supplementation and COVID-19 infection and mortality

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9653496/pdf/41598_2022_Article_24053.pdf

Vitamin D and COVID-19: An Overview of Recent Evidence

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8509048/pdf/ijms-22-10559.pdf

COVID-19 and Vitamin D- a Systematic Review

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8937591/pdf/sjph-61-124.pdf

Protective Effect of Vitamin D Supplementation on COVID-19-Related Intensive Care Hospitalization and
Mortality: Definitive Evidence from Meta-Analysis and Trial Sequential Analysis

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9864223/pdf/pharmaceuticals-16-00130.pdf