This systematic meta-analysis paper[1] may be more convincing. The popular youtube COVID-commentating Dr. John Campbell did a review of it about a month ago[2]

This systematic meta-analysis paper[1] may be more convincing. The popular youtube COVID-commentating Dr. John Campbell did a review of it about a month ago[2] and has some good comments on the meaningful statistical power and experiment design. The overall takeaway is this: in people with Vitamin D deficiency (which is very, very common), continuous daily supplementation can lead to up to a 70% reduction in contracted viral respiratory infections. It has a smaller effect the less deficient you are, and is not associated with any adverse effects. 1 - https://www.bmj.com/content/356/bmj.i6583 https://www.bmj.com/content/356/bmj.i6583 2 - https://www.youtube.com/watch?v=W5yVGmfivAk https://www.youtube.com/watch?v=W5yVGmfivAk