My SiL and BiL are like this too. They won’t go out until the UK is Covid free.
No underlying health conditions (that we know of), he’s early 50s, she’s just turned 40.
They are going out for walks, but go really late at night when there are less people are around. They run a business together working from home and get everything delivered. They desperately need some maintenance work done on their house but won’t allow anyone in, they won’t meet with anyone outside, won’t have takeaways delivered.
They won’t have the vaccine - BiL is eligible (due to his age), but SiL isn’t quite yet.
BiL is a bit conspiracy theorist about COVID (he always has been tbh) - he thinks the vaccines have chips in that will track and control us, and SiL says that she won’t have one either.
SiL has always been outgoing and extroverted, travels a lot, always out, loves clubbing and has a very active social life. BiL never went out with her, never went travelling with her or anything like that either, but never seemed controlling as she’s always done her own thing and he’s never stopped her in the past.
It is worrying, but the only contact anyone has with them is FaceTime/phone and she says that everything is fine - she seems her usual self when chatting but you can’t really tell over FaceTime. Other SiL has tried popping round but they won’t answer the door, and won’t even have a socially distanced cup of tea in their garden so it’s hard to get to the bottom of it.
SiL says she accepts that if she doesn’t have the vaccine she probably won’t be able to go travelling again, no pubs/clubs if they bring in vaccine passports which is so unlike her that it’s quite worrying and it’s difficult to get a handle on what’s going on with them