I'm not sure how to interpret those % effectiveness figures. But I wouldn't think 17% effective necessarily means that 83% of people who get the shot will still get the flu. That still doesn't take into account the variables of actually being directly exposed AND not be using proper hand washing techniques AND other factor which increase or decrease your risk, etc.
I have no medical background (therefore, I may not be characterizing this properly) but up until recently, I did not realize that the flu was strictly a respiratory disease. I'd always heard about people talking about stomach or intestinal flu and didn't know that this wasn't really "the flu" or some other variation of it.
I have gotten a flu shot every year for at least the past 10 or 12 years and I've maybe had the real flu once in that span... maybe! Now I've had several encounters with stuffy nose and sore throat - so maybe those were minor cases of the flu and I just don't know any better, but I tend to believe that these were either allergies or common cold. I've also had numerous bouts of the 24-36 hour violent stomach and intestinal expulsions -- all along thinking that was what my flu shot was supposed to prevent.
So I think that my experience with the flu shot has been about 92% effective or better (again depending on whether my sniffles and coughs were minor flu or just colds). But I still believe that effectiveness rating doesn't really account for incidents of exposure. Other than last week when I was experiencing a minor headache and very slight throat irritation (neither of which turned into any actual pain requiring medications to get rid of - so not the flu in my best guess) I have been taking communion wine every Sunday of this flu season and have been holding and shaking hands with those arounds me during the appropriate times during Mass.
And generally speaking I am a very frequent face/mouth toucher, eye rubber, and nose itcher - often without even realizing I am doing it. I am an average hand washer (far from overboard and probably still not nearly as much as I should during flu season). Yet with all of this :::knocking on wood::: I still haven't picked up any flu.
Do I attribute this 100% to having had a flu shot? Certainly not. Do I believe having the flu shot has helped in some way? Absolutely!