well, there are a lot of factors that influence which person gets sick, and who doesn't- my first son has ecxema and catches everything under the sun, my second son is almost always healthy and if he does catch stuff it fizzles out soon, and they were both exclusively breastfed forever... my dd who was mostly bf but had some formula time with her grandma (before i got militant) never gets sick.
same diets, same environment. different genes. the flu can be nasty stuff, so i have a healthy respect for it, no pun intended.
great living conditions no doubt help keep us healthy, but are not going to keep everyone from dying from a really nasty virus that happens along... that said, no way do we inject (or inhale
: ) that crap into our bodies. never had one, never will.