Flu vaccine game theory

One of the things people don't know about me is that, in college, I minored in Humanities -- which, if you don't understand, roughly translates into me minoring in being a dilettante. To complete the minor, I had to complete a certain number of units in a certain number of disciplines. Since it's been 15 years, I can only remember four of them -- Art History, Theater, Spanish (Yes, I can translate Spanish poetry -- or in my case, lyrics to pop songs), and Economics.

(Cue "One of these things is not like the other.")

Yes, Economics. Which mostly means that I was the only hippie in a class full of libertarians studying Law and Economics. But which also means that I have a slightly better-than-average understanding of concepts like game theory.

Last night, I was thinking about this in the context of the flu vaccine. You see, I was out with a friend and mentioned that I got my flu shot, and she, in turn, noted that she did not plan on getting a flu shot this year because she never gets the flu. My mind started racing with the implications.

Ideally, the flu vaccine works best when large populations are vaccinated. But it bears a cost -- money, time, pain. Moreover, people can't really prove that the flu shot works -- if they get the flu shot and don't get the flu, they can't just assume that it worked. They may have a natural immunity or may not have been exposed to the virus. But if they get the vaccine and it doesn't work, they know.

So what is the vaccine other than a way of hedging your bet? If you decide not to get the flu vaccine, aren't you really just counting on the probability that the people you come in contact with are not contagious, i.e. got their vaccine?

Clearly some economist or public policy grad student out there needs to contemplate this more fully.