Dr.s are treating covid with D and Zink as well as other stuff I guess. It is a known fact that those 2 vitamins do a fantastic job of strengthening the immune system. I started taking those 4-5 years ago as per my Dr.s orders for other reasons but I take a 4000IU of D and 100mg Z every morning along with Turmeric, E, B complex and Omega 3 fish oil and my health has been improved since. The Turmeric is for inflamation control all over as I have nerve damage in my legs n feet (neuropathy) and it maybe helping to prevent further old man aches and pains or not but I take it.According to a couple of doctors I see, there are apparently some indications that taking Vit D and Zinc (cold-eze, for example) help with resistance. Have also heard about the blood type bit.