I was aware they do not counter every strain, but they are, at least in their current incarnation designed to help stimulate the natural immune response to a heightened level and encode it with the likely threats it is facing. With regard to the people who become ill after receiving them, that is a fairly normal response that they receive a very mild case of the illness or similar effect. It really depends upon the culture used as some are still partially alive but in limited quantities or are sterilized and dead as you said. I have still managed to never fall ill to it; the last thing that I was actually incapacitated by was poisoning, which was an interesting experience to say the least.
Either way I, as someone forced to spend extended periods with people much to my chagrin, am not fond of people being ill ever and am just fairly unsympathetic to begin with. The sort of scenario where I find myself asking, "Why are you here when you are sick? All you are going to do is contaminate everything and force me to clean it twice in one day."
And yes, I am one of those who avoid hospitals not because of any distrust of medicine, something I am somewhat trained in, but because there are ill people there and the atmosphere is exceedingly unsettling.