I will be the first to admit that the issue of flu shots is contentious:  on the one hand, my belief is that they are not effective at preventing the flu, on the other - they do seem to mitigate some of the concomitant health problems (bronchitis, penumonia) which can be killers. 

However, I do find it interesting that apparently the proponents of flu shots have to exaggerate their results to get people to comply.

Benefits Of Flu Vaccine Substantially Overestimated Says Study

The Vitamin Lady writes about natural ways to protect against the Flu