We had several years where the four of us just passed bugs back and forth, couldn't seem to get well. Finally I started gathering tips on helping cut back on flu and was able to break the cycle. We still get sick but we don't pass it as much and were not sick all winter. Mind you, we're still dealing with major fatigue issues, but not so much cold and flus. Here was the best tips I received:
1) don't brush your teeth in the bathroom or leave toothbrushes in the bathroom. Every time a toilet flushes, it disperses millions of particles ino the air which land on your toohbrush.
2) carry a stainless steal water bottle and never use a drinking fountain
3) remove BPA plastics from your home and especially avoid cooking in them. They suppress the immune system as well as thinning the epigenetic layers of DNA.
4) get an air filter with UVC light.
5) up your antioxidants....but I suspect you're already doing this.
Hope this helps.