Yes having good vitamin D levels is good, as low levels are associated with more severe CV-19 disease. Seems to be related to the fact that CV-19 is a blood an

Yes having good vitamin D levels is good, as low levels are associated with more severe CV-19 disease. Seems to be related to the fact that CV-19 is a blood and organ disease (that happens to have airborne transmission), micro-clotting is a big effect, and Vit-D has some anticoagulant effects. But it will NOT prevent infection. A properly fitted N95/N99 mask will. It takes about 700 viral particles (early strains) entering the airways to start an infection (obviously variance involved). Cutting out 95-99% of the particles you breath in an exposure event gives you 20X to 100X margin to prevent infection. When good masks are generally used, those effects are multiplied together, as the contagious person's spreading of viruse particles is reduced by 20-100X, and your mask reduces that attenuated stream by another 20-100X. These effects are why the R0 of all airborne diseases is cut when most people take measures. We can see this because while the spread of the more contagious CV-19 was reduced, entire strains of influenza went EXTINCT. Wiped out forever. They could thrive in an unmasked population, but died out when people even masked badly and inconsistently.