Took me a while to actually get around to reading up on this, but nursetim's comment is an important one since some people may have the impression that the flu is some invincible superbug now. Although the most common flu strain this season appears almost universally resistant to Tamiflu, it shows no sign of resistance to a different anti-viral, Relenza. In addition, all these Tamiflu-resistant samples were susceptible to the older anti-virals, too.

I would disagree with this statement that you can't effectively make a useful vaccine because the flu will be different by the time flu season comes around. This season's flu vaccine is antigenically well matched to the actual circulating strains.

However, before someone jumps in and says, "I got a flu shot but I still go the flu!" there are all kinds of explanations for that. It's important that people understand what they should and shouldn't expect from a flu shot. Unfortunately, vaccination campaigns are often too simplistic, and people aren't informed about realistic expectations.

The most common reason why someone "still got sick" is that they didn't actually catch the flu, but instead, some other disease that shares flu-like symptoms. And getting a flu shot does not confer 100% protection against getting any symptoms at all even if you got a perfectly matching vaccine. Immunity is a complicated thing and getting a well-matched vaccine is only one of the characteristics that keeps you from getting sick. You might still get a fever, body aches, etc. but in general, it probably would have been a lot worse if you hadn't had the shot. Of course, the best outcome after getting a flu shot is that you don't come down with it even when exposed to the virus.