> it should be equally obvious
Clearly it is not obvious, considering most people have never spent a significant amount of time thinking about how infectious diseases work.
> What's that? Do I hear the "There's no evidence for immunity to covid-19" crowd in the distance? I'm getting a bit tired of that line, but if someone wants me to dismantle that argument (again) I am happy to.
Why make a snarky, coy comment like this? If you have something to say about immunity then just say it. In fact the WHO are among those who make this claim[0], so "dismantle" away.
[0]: https://www.who.int/news-room/commentaries/detail/immunity-p...