Any advice on how to boost my immune system?

[SereneCapybara]

I caught a norovirus in late August last year and since then have had Covid, a heavy cold two bouts of flu - one lasting three weeks, and tonsillitis. This week I have been ill again - sore throat, shivers, aches, exhaustion, back in bed, taking endless doses of ibuprofen and paracetamol to stop the sore throat.

It's really wearing me down, being ill so often. Had to cancel so many plans, scale back work and give up nearly all my interests as I have no energy and can't focus.

Can anyone advise on what I should do differently to boost my immune system?
I eat healthily - lots of veg every day and all fresh food - almost no processed stuff. I walk most days when well, do weight training, take supplements of iron, B vits and when ill I also take Berrocca.

What else should I be doing/eating/trying to ensure I don't get ill as often this year?

I do eat meat a few times a week, but not every day. But blood tests in the past have shown B12 deficiency.

@LittleGreenDragons that seems like really high strength vitamin d3, is it still safe?! At the moment I take 2500 dr vegan d3 but no k, is it worth trying this? Do you feel better taking it?

How are you feeling now OP?

You can safely take up to 5,000 iu a day but I'm conscious that level is probably more for those who are house/bed bound and can't access it naturally, but anything under is fine. 1,000 is the dose recommended for fit and healthy people during the winter months as a maintenance dose. Bear in mind that GPs can prescribe it at 20,000 if you are deficient so 5,000 really is okay as an over the counter build up dose.

However it should be taken with Vitamin K (the same as you need Vitamin C with iron), for better absorption. If your body can't absorb it properly then you are wasting money, time and effort in taking it.