In the early days of Covid infections in India research found that patients with optimum vitamin D levels not only survived infection but were less likely to require hospitalisation or breathing assistance. Additional evidence...
"Contrary to widely held views, the research team discovered that both types of vitamin D did not have the same effect. They found evidence that vitamin D3 had a modifying effect on the immune system that could fortify the body against viral and bacterial diseases" https://scitechdaily.com/study-finds-vitamin-d3-important-fo...
Instead the thesis is something like "Outdoor light makes you generally healthier therefore you're more likely to survive a COVID-19 infection."