I read they were using intravenous Vitamin C in China with good success. Don’t have references, though I believe I’ve seen them.
I also wonder about vitamin D and A. As well as NAC.
I ordered the sublingual Vitamin C 3000mg liquid. It is now out of stock and they don’t know when it will be replenished.
Three Intravenous Vitamin C Research Studies Approved for Treating COVID-19