Quite a lot of discussion showing their herd immunity didn't work.Sweden, have stopped shielding, but they've given guide lines to the shielders, to reduce there risk of catching and the country is much nearer 100% have had it, so less people able to spread it, so safer, where as UK have slowed it enough to keep it around to get them.
As I said, lock away the at risk wait for it to get everywhere, then have an Orgy day everyone must attend, 4 weeks later everyone would of had it, recovered and it'd all be over and safe for the at risk to come out much sooner.
Interesting article: https://time.com/5899432/sweden-coronovirus-disaster/