Travel to Z

Not sure I’d call it compelling. Only 253 patients had Vitamin D levels measured of those measured some measurements were 2 years before their positive Covid test. It hard to imagine that a low Vitamin D level 2 years ago had anything to do with developing Covid. It would be more convincing if the levels were obtained a few months before the positive test. There is also the problem with comorbidities possibly playing a part.
While they claim statistical significance, they do it by including all of the Vitamin D deficient patients, some of which (how many?) had 2 year old vitamin D levels.

So while it is interesting, in my mind it is a long way from proving anything. That said, unless taken in large doses Vitamin D can’t hurt you, unless, of course, you have a history of kidney stones, which could increase their frequency.