Hilary may have viral pneumonia and the inoculation would not protect against that. It isn't usually serious and many of us may have had it and not known, a cold and cough, the cough disappears, we feel lousy and debilitated and then perk up. I've had it at least once, it was diagnosed on chest X-ray which I had to rule out something else. That was at least twenty five years ago but I was OK, didn't have any treatment. (Well I woz a bit more lively in those days so things were shaken off more easily
. )
If Mrs Clinton was not doing what she is doing at present, ie charging about all over the place and probably not sleeping particularly well, she may well not have noticed anything amiss so let's wait and see what the pneumonia actually is. She needs to boost her immune system.
As the above poster said, both President Roosevelt and Kennedy had chronic health problems and it didn't stop them. I know Hilary has been plagued with illness on and off for a while but I would hate something like a simple infection to ruin her chances, whatever I may think of her.
I saw Trump on the news last night and he was launching a personal attack on Hilary Clinton, saying she was of poor moral character or something like that. I thought that was very strong! They all get personal but surely there are limits.