Oh Sue how annoying, unfortunate, and bloody inconvenient! Tell that chest infection of yours to bugger off!!!!! I really hope you can get some caring for yourself as well. While I know you are caring for Nat you have to take care of yourself as much as you can so call on all your available resources/support so you can be back to your old self as soon as possible. Can they get a community nurse out to Nat for the injection rather than have you take her to the hospital? My other suggestion is to wear a mask. Very common for people unwell in Japan to wear masks which is totally polite of them if you ask me. So hoping you get well soon.
All the best, Nadine