The UK's health services are struggling at the moment.
So can the conclusion be that vitamin D does not work as expected? Or is the conclusion that still not enough people are taking vitamin D, and its usefulness should be better communicated?
The reasons for UK health services failing have little or no connection to vitamin D.
Vitamin D has shown signs that it slows down / makes covid less deadly.
Because we don't understand: who is taking it, in what amounts, local weather, what the numbers would be without it we can't assume anything from them struggling.
The amount recommended is insufficient for most people to get to the level where (correlation) has shown significantly reduced risk - that is >30 ng/ml (>75 nmol/l)
Another thing that is tricky is that it really depends how much you need to take on what your levels are personally. We know that the amounts they recommend are completely long term safe for everyone and long term good enough to avoid severe deficiency. But for most people there will still be insuficiency - the necessary average is actually around 2000 IU (for some people it should be up to 4000 IU, others less)
So can the conclusion be that vitamin D does not work as expected? Or is the conclusion that still not enough people are taking vitamin D, and its usefulness should be better communicated?