Yeah, I think the benefits of Vitamin D are pretty clear, so while it certainly isn't a vaccine substitute, it's a good supplement. I got vaxxed and also been taking Vitamin D supplements. Just getting out in the sun helps too.
For sure, sun exposure a little before noon has been a regular thing for me for a while, even before I started fasting. Even when I had covid back in early August, I would be sure to go outside in the sun around 11am.