Getting sick occasionally is good for your immune system if you do not have a condition like your wife.
Key word being occasionally, and also not with a disease that causes serious health complications, cognitive decline, and that itself damages your immune system.
COVID linked to 65% of new onset cognitive impairment, dementia
Every COVID Infection Increases Your Risk of Long COVID, Study Warns
SARS-CoV-2 infection weakens immune-cell response to vaccination
Yes, Everyone Really Is Sick a Lot More Often After Covid
Cognitive performance of post-covid patients in mild, moderate, and severe clinical situations
Being outside is good for your immune system. Being near other people is unnecessary.
Exposure to one virus rarely leads to a resistance to another one. That’s why they have a new flu vaccine every year even though they’re all closely related. Cow pox immunizating against small pox was a fluke
It’s more about being exposed to everyday bacteria, pollen, and hot/cold cycling that gives your immune system exercise.