I caught a lot of colds when I was in my 20s through mid-30s, and I was very active then. Perhaps too active - I'm sure I was over-trained most of the time, as there was no access to coaches for the sports I was doing.
Now I'm in my 50s and have had one cold in two years, even as a lot of people in my office are battling the same long-running cold for weeks and weeks. I tell them it's the chlorine, killing all the bacteria in my upper respiratory tract. Especially after my epic battles with the flip turn.
Oddly, this resistance to infections seems to have started with menopause. Go figure.