I personally have long suspected that the “cure” for various ailments can be found in the people who don’t get it. There are people who never get the common cold, flu, cancer, whatever. It’s almost impossible to differentiate between good fortune and immunity, though.
Statistically I would guess that due to the wide variation in individual genetics that there are people who are immune to string viruses but don’t know it.
For the first forty years of my life....I had a twice-a-year cold episode. Then one day, I started taking vitamin C (in pill, juice, and orange form), and for the ten years...I’d take a guess that I’ve only had a cold three times. Now, I admit....I’m more picky about shaking hands and sanitizing after touching public doors/surfaces. I also spot people with colds and stay a good six feet away. I lessen my use of public restaurants and pubs. And I don’t spend a lot of time out in some freezing environment for hours and hours.