Personally, I think a lot has to do if you are around kids.
Once you stop being around kids, you don’t get sick as much.
I hated the winter formal at my kids high school. For 7 years, one of my kids would get sick after that dance.
My kids also did theater, and they would always get sick during shiws.
Now, they are in college, so at least I avoid their illnesses.
D-3. I doesn’t much matter whence th flu or cold originates. Take the D-3 supps and you will not get the viruses. 5000 i.u. a day seems to be an effective amount- les perhaps, more certainly. The reason Flu etc. is almost entirely a winter phenomenon is the lack of sunshine on the skin.