Wikipedia defines common sense as “knowledge, judgement, and taste which is more or less universal and which is held more or less without reflection or argument”
Try to avoid using this topic to express niche or unpopular opinions (they’re a dime a dozen) but instead consider provable intuitive facts.
Another variation of that is claiming how getting sick repeatedly is somehow beneficial for getting a strong immune system. That ignores research, as children who have a lot of common infections early in life have higher risk of moderate to severe infections and antibiotic use throughout childhood. That also ignores viruses for which a durable immunity isn’t currently possible, such as COVID.
EDIT: Basically the immunity system doesn’t work like a muscle.
I think the immune system can be likened to a muscle if someone really wants to go with that metaphor, but only if you consider vaccines to be the gym and getting sick is uncontrollable and dangerous physical exertion. So, wanting to develop natural immunity is like wanting to get into street fights to build arm strength. It might kinda work, but you’ll also be in a lot of unnecessary danger.