If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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1. Please add the 'open_thread' tag.
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There are over 100 strains of the common cold. If you gain immunity to one, this will not significantly decrease your chance of catching a cold in the far future. On the other hand, good hygiene will significantly decrease your chance of being infected by most contagious diseases.
It's at least plausible that people become less vulnerable to colds as they get older.
http://www.nytimes.com/2013/08/06/science/can-immunity-to-the-common-cold-come-with-age.html?_r=0