If you have healthy, low-risk people intentionally get the disease (from a single variant which you keep in good stock) and then strictly isolate/quarantine until they get better, that'd be a potential strategy. It's probably the best way to get overall immunity high enough that COVID would burn out... ...of course, this is basically the same as a super crappy vaccine. Vaccination would be way better. But back when people were poo-pooing the possibility of a fast vaccine development, it almost felt tempting to just do this and get it over with.

Because the virus wouldn't be spreading beyond the host that got it, the risk of mutation would be small.

(IMHO, we should've just massively accelerated vaccine development... even just a couple months would've saved lots of lives. If you're willing to try the strategy in my post, then accelerating vaccine approval would probably be no worse morally and probably a lot better.)