There appears to be a strong correlation between the severity of COVID-19 and Vitamin D levels. This makes sense since vitamin D regulates the immune system. Vitamin D regulates cytokines and blood clotting. The most dangerous symptoms of COVID19 are "cytokine storms" (aka inflammation) and blood clotting.
Sunlight turns cholesterol in the skin into vitamin D. This is probably why the death rate is down in the US while the death rate appears to be on the rise in Brazil and Argentina. The death rate is likely to increase in the US in the Fall and Winter.
Anyway, it seems to me that the thing we need to do is improve the American diet and for people to get some sun. The best time to catch rays is at noon. 10 minutes will do.