I have been so fortunate in this area, since the accident, I have not been sick once. I think that because my body is concentrating on healing, it has my immune system on high alert also. Another factor, now that I am retired, I no longer have to touch the keyboards of co-workers who are "no longer contagious.
I do have one bit of advice, It may sound crazy, coat your feet with Vicks Vapo-Rub then put on a pair of socks before you go to bed at night. Don't knock it till you've tried it, it works for any cold symptoms.