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.
… in time to keep you alive. I mean, given enough time, the body will figure things out. Vaccines are cheat-sheets to cut that time so it’s accomplished before the host dies.
Or overreact, and kill you that way. Viral fevers, allergies and septic shock are all examples.
Evolution is not a human designer. It’s produces an endless pile of kludges that ends up working well enough. Although, in some ways that’s even more impressive.