There is the pervasive myth that needs to be busted. (Someone shared it with me just this week!) The myth is that we are healthier because we get more infections and that builds our immune system.
The immune system isn't a muscle. Yes, infections impart some immunity (sometimes long-lived and sometimes, as with COVID, quite brief.) But each infection carries more risks from acute and chronic illness than the meager benefits imparted. (1/4)