I hear you about being careful. I try to read every opinion about the most likely ingress into your system. So far it seems to me the the "experts" keep referring to your nose as the primary way it infiltrates and infects. I haven't read where they think directly getting into your lungs does it. Perhaps it multiplies in your nose and it gets into your lungs by breathing through your nose, since that's the way we normally breathe. If anyone's read more, let me know. To that end, I made custom nose filters out of 4-ply HEPA filter material that I insert into commercial "2.5" nose dust filters, AND I use the same material to form masks that fits inside a supposed "KN95" mask. Doctors and nurses still catch it wearing N95 masks, so it seems it's not good enough to wear just them.
There are a lot more younger people getting seriously ill so I wouldn't rely on just age or physical condition. The latest I've read is they think it's genetic, because perfectly healthy young people are dying from it while older people, like the spouses of seniors with it don't even get sick. It makes sense to me, that's it's your chemical makeup that determines if you are infected, whether you get symptoms, get seriously ill, or die. When it first got the people on cruise ships there was a guy with a superspreader amount of virus in his nose him yet he didn't have any symptoms. The only think I can surmise is the virus was unable to attach to his cells, because I believe even making a ton of antibodies from an infection won't keeping you from getting symptoms. Maybe with the vaccine, but I don't see it happening on your own, because spouses that don't get sick don't seem to have a lot of antibodies. I'd call it Chinese roulette.