A good resource for checking real-time studies on a variety of treatments for the new corona/covid-virus is c19early.com. They gather studies on favored pharmaceuticals, and also much cheaper treatments like (forbidden) pharmaceuticals, vitamins, minerals, plants, plant-extracts, etc.
The image above is a summary of all the best single treatment options, ordered according to efficacy at all stages of the disease. As you can see, there are many supplements on the list and they fare very well. At least Nigella Sativa, Quercetin, Curcumin, Zinc, Vitamins A, D and C, Melatonin, Probiotics, etc are available to the public without big pharma intrusion. NAC has also been shown to be effective, but is missing from this list.
We could start marketing these in this time on C-19 as a scientifically tested treatment option. Also, keep in mind these are single treatment studies. In right combination these supplements could be much more effective.
P.S. Natural immunity is still the way to go when it comes to individual health, collective health and, of course, when it comes to resisting medical tyranny.