That's a mistake if you have a +-normal immunity. Ie childhood immunity is in desperate need of opponent so it can train itself. If you keep your kids in sterile environment, its more or less guaranteed they will end up with nasty allergies for the rest of their lives. I would expect this should be true in lesser form for adults too.

Anyway it doesn't make sense at all, most of the time folks are sick its not flu - its due to bacteria/viruses we already have in ie throat or nasal area that spot a weak moment (ie getting cold or eating too cold food) and attack. I basically get sick only like that during winter. One time I had pretty bad case of food poisoning from stale mayo and was so weak, I had sore throat and running nose almost immediately.