I am sorry to hear about your wife. I hate to give any false hope, but I highly recommend that you make sure she has plenty of Vitamin D (and you do too) in her system without going overboard. Personally, I've been taking and recommending 10,000 iu to anyone who will listen.
Vitamin D is often touted as fixing or preventing everything, and I believe that is way overblown. And the data available for Covid is less than proof, but I feel it is very compelling with little risk for the potential gain.
This study from March-April shows a statistical correlation only, but that correlation basically says that 85% of covid patients with normal Vitamin D levels had mild cases and only 7.2% of these patients had severe cases. In contrast, 72.7% of the vitamin D deficient patients were severe cases and only 1.4% were mild. That, to me, was pretty darned compelling even though it doesn't prove causation.
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A more recent study in the last couple of weeks suggests this is more than correlation:
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There are currently about 20 ongoing studies on Vitamin D and Covid - some testing if giving patients vitamin D after they have been diagnosed with Covid improves outcomes. The risk of taking 5,000 or 10,0000 iu/day is really small in an otherwise healthy population and in my non-medical opinion, the reward could potentially make such small risks well worth it.