Yes, I've talked about that in other posts but no, you won't see the authorities implementing vitamin D-boosting plans.

Vitamin D boost your inmune system. People with high vitamin D levels very rarely get colds or the flu and, if they do, they have few symptoms and of short duration. This can also be applied to Covid: you can find dozens of studies in Pubmed showing that people with high vitamin D levels either don't get COVID or they have few symptoms. On the contrary, people most of those who die from COVID have low to very low vitamin D levels.

You can find many scientiphic articles on: https://vitamindwiki.com/

Big pharma isn't interested in this because vitamin D is free if you get it from the sun and supplements can be bought in herbal stores.