For as long as I can remember (at least the last 5 years), I've gotten the common cold 2 times every winter. This has been eerily consistent, despite all the protective measures I've put in place (washing my hands regularly, using hand sanitizer, trying to avoid sick people) - on top of all my regular healthy habits (drinking plenty of fluid, taking vitamins, getting enough sleep).

So, it's rather surprising that suddenly this year I went the entire winter without coming down with a cold. I suppose it could just be luck, though I think this is the first year I've been taking a vitamin D supplement every day. I've also been getting less exercise than I had the past couple years (because I've been walking outside less). I know they say that there are thousands of strains of the common cold, but maybe they miscounted and I've actually gotten and become immune to all of them.