Why can we not gain immunity to the common cold?

Chris - I wish I knew the answer to that. It's actually just simple numbers. There are two reasons for this. One is to be immune to something, your immune system has to see it in the first place. So you have to be infected with the thing, so you then learn to neutralize it in the future. Now, that would be simple if there was one virus, but in fact there are hundreds.If you look at the rhinovirus family, which is the cause of the common cold, around most of the year, there is about a hundred of those. If you look at the enterovirus family, there's about a hundred of those. There is 50 or 40 adenoviruses, many of which cause upper respiratory and eye infections. Then there are the corona viruses, the parainfluenza viruses, the influenza viruses and to add insult to injury, these viruses also mutate. So not only are there hundreds of them around for you to get your immune system's head around but also they are moving target. They are changing their molecular appearance, so even if you have learned to recognize it, there's no guarantee that you'll recognize it again the next time. And given that there are all these hundreds of viruses and the average person gets about two or three colds per year, that's three life times worth of cold infections before you've actually got any chance of being immune to all of them, by which time they probably have changed.So, I don't think there's really any prospect of ever being able to cure the common cold with the exception that what scientist including Steven Legit who is a researcher of University of Maryland had done, is they've sequenced genetically all of the rhinoviruses so far. And they know how they divide up to a little subfamilies and it might be that if you a made a vaccine based around some members of some of those subfamilies, then every time you immunize someone who gets one of the subfamilies you are protected against all the other members of that family. So you could make a vaccine but it would have probably be based around lots and lots a different members and probably be unfeasible. Who knows, let's hope though that we come up with some kind of common cold cure soon because since you have children you're into a whole different ball game.