I don't believe there is anything cut and dried as

I don't believe there is anything cut and dried as it relates to COVID-19. It seems that every day another unknown about the disease comes to light. Why does an apparently healthy 45 yr. old individual succumb to the disease, but a 75 yr. old with all the issue of aging, survives it and returns to home. What is the "mental fog" all about. Why are there different strains? How many more strains are out there. How long will the vaccines provide immunity? How will the vaccine affect me a year from now, 5 years from now? How will COVID affect me a year from now, even if I recover.

To me those are question that are complex with only partial or no know answers. I'm sure others can add to the list.