I've had "The Something" once, in the spring of 2020. It was pretty horrid. I got over it, by myself, at home. I had it again, recently, about 16 months later. I felt "somewhat sick," and it was basically out of here in 72 hours.
My experience is that natural immunity works... just the same as most of our serious childhood illnesses.
But that's my experience; people should be free to do what they want.
=^..^=