At risk of irritating John, I should to clear one or two things up about vitamin D.

In the UK, between March and October, you can get all the vitamin D you need by going into the sunshine for fifteen or twenty minutes a few times a week. This applies if you expose enough skin - arms, legs, heads, sort of thing, but it doesn't apply if you're plastered in sunscreen or dressed up to the hilt. In the other months you need to get the vitamin from food. Or supplements. If you eat oily fish, eggs or red meat, no problem. These days, breakfast cereals and those soya and oat milks can be great sources - read the label.

There is next to no evidence that taking vitamin D will stop you from catching "the virus" or make you less sick if you do catch it. Sorry, guys!

Opinion-only time: I hate the supplement industry. My conviction is that supplements are at best a waste of money for all except for a few vulnerable people. If you're a vegan, you have a self-inflicted B12 issue. Over to you. And your diet needs to to be really good with regard to fresh or frozen greens if you want to get sufficient folate, and folate is a bit of a red flag for pregnant women. Apart from that, chuck you multivitamins in the bin and deprive those cynical pill-pushers of their ill-gotten profits.