Most countries in the northern hemisphere recommend supplimenting vitamin d over the winter anyway.

Seems like a no brainer to encourage people to start taking vitamin d now as it clearly at least has a small positive effect against covid

TLDR of this referenced article: In each and every scenario and study that is examined there is a general consensus that Vitamin D deficiency may be correlated to increased susceptibility or severity of COVID-19. The final conclusion is a word of caution that this news may cause some people to load up on Vitamin D at dangerous levels. However it also states that taking a small daily dose IS actually a good idea during Covid. The dose recommended in the article for pretty much anyone is 1000 IU during Covid.