I've got diabetes, OH has cancer, we're both mid 50s and both have impaired immunity due to our conditions.
We do our best to avoid public transport and crowded places anyway, and have done for years since our conditions were diagnosed. We still live a reasonably "normal" life, but don't deliberately put ourselves in harm's way.
For example, we avoid Terminal 3 at Manchester Airport like the plague. It's an overcrowded tiny hell hole squeezed into a corner of the airport (old domestic terminal). We choose flights out of terminal 2 instead - yes, costs more and limits our holiday options, but it's a much more pleasant experience, far more spread out, far less busy, etc. When we choose seats on the plane, we either choose front row or back row so we can be on last, off first, and surrounded by fewer people, and usually do short flights. Never seen any airport abroad anywhere near as crowded/busy as Man terminal 3 - even "hubs" such as Amsterdam are far better designed, more spread out, etc.
Same with shopping - we avoid busy days like Saturdays and Sundays and shop at quiet times when the shops/malls are virtually empty.
We never eat or touch our faces without having washed our hands first, especially if we've been out, touching door handles, holding handrails or shopping trolleys etc.
When on holiday, first thing we do is go around wiping down surfaces, handles, taps, etc., and we tend not to let the "maid" in every day. Many years ago, we were in when the maid came in to clean and were horrified to realise she only had one cloth in her hand, which she used to wipe the kitchen area after she'd been upstairs wiping the bathroom! - she was doing more harm than good spreading germs around, and she didn't change the cloth when she went in next door!
Hopefully, the corona virus will at least make people think and increase awareness of hygiene and cleanliness. I can't believe people still aren't washing their hands after they've been to the loo in public toilets - nor people sneezing away in public without making any attempt at all to catch it in a tissue or their sleeve. Still lots of dirty buggers about.