A megadose to bump vitamin D levels has been used for years, perhaps decades, and verified to affect blood levels - a friend’s doctor recommended to them a while ago 60,000IU per month, 20,000/week or 1000/day. I don’t know the exact logic, but it’s not new.

Whether or not such a bump gives the same benefits as slow ramping (and if it delivers then more quickly or not) is something I haven’t found any studies on - but I have found in the past studies indicating sun exposure is better than supplements for the same attained blood vitamin D levels (not surprising, as vitamin D is far from the only result of sun exposure)

Of course, starting now is better than starting later to get the effects.

That said, I can totally imagine people downing a megadose of vitamin D, declaring themselves immune, and going out to lick doorknobs immediately.

Well I've read things that suggest eating covid won't hurt you. May be similar to HIV where the official advice is not to slosh it around your mouth endlessly but either spit or swallow immediately?

They would overdose on D. Too much of that vitamin from pill is bad for you.

This situation has being going on for longer than days or weeks too.