If you’re a lay person, I don’t know how much more clearly the case for getting your seasonal flu, swine flu, and pneumonia shots can be made than this: a compelling statistical correlation and quotes from two leading experts. Here’s the statistical correlation (which appeared in a recent Atlantic Monthly article for November 2009):
[R]esearchers studying the impact of flu vaccination typically look at deaths from all causes during flu season, and compare the vaccinated and unvaccinated populations. Such comparisons have shown a dramatic difference in mortality between these two groups: study after study has found that people who get a flu shot in the fall are about half as likely to die that winter—from any cause—as people who do not. Get your flu shot each year, the literature suggests, and you will dramatically reduce your chance of dying during flu season.
And here, in the same article, are quotes from two leading experts on virology who advise flu vaccination:
Nancy Cox, the CDC’s influenza division chief, says flatly, “The flu vaccine is the best way to protect against flu.” Anthony Fauci, a physician and the director of the National Institute of Allergy and Infectious Diseases at the NIH, where much of the basic science of flu vaccination has been worked out, says, “I have no doubt that it is effective in conferring some degree of protection. To say otherwise is a minority view.”
You’re certainly free to ignore such a powerful statistical correlation and majority medical opinion on the importance of getting flu vaccinations, but why, if you’re not an expert in the field of virology, would you do so?
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Both quotes above come from “Shots in the Dark”, an article that appeared in the November 2009 edition of Atlantic Monthly.
Prometheus Unbound 
expert opinion is not evidence. The ONLY valid way to judge effectiveness is through a randomized controlled trial which is very easy to do. Evidently there are no such trials demonstrating effectiveness of flu vaccines.
Correlations, even powerful ones, do not prove causation. Evidently, those who choose to get flu shots are healthier on the average than those who do not. This can easily produce the results cited.
Elliot:
Unless you are a physician, you should listen to experts in the field. People should do what their doctors advise them to do. In the case of the flu shot, doctors advise it, so do it—or go to medical school. They’re not trying to hurt you, but trying to help you.
Also, you have a moral obligation to your community not to be glib about communicable disease prevention. If you must indulge in conspiracy theories and armchair theorizing, do so in subject areas where they are likely to cause less harm to yourself and others.
—Santi
Few physicians are scientists and this is a scientific and statistical question. To say that one should simply do what doctors advise is just dumb. I’d like to know what the evidence for effectiveness is. Cohort studies do not impress me; they have often been shown to be wrong when randomized controlled studies are preformed. Jefferson says that there is little evidence. As a statistician, I’m impressed by his arguments. See
http://www.bmj.com/cgi/content/full/333/7574/912
Elliot:
Jefferson is a journalist. He is not a physician, nor is he a virologist. Those with the expertise to know the nuances of the subject say “get your flu shot.” If flu shots are ineffective, then the issue will be settled in peer reviewed journal articles written by researchers who can muster evidence in such a way as to persuade the majority of their fellow researchers that vaccination does not work. Needless to say, that’s not where we’re at. Until the CDC provides a different recommendation, lay citizens should continue to get their vaccinations. It is astonishingly ignorant of you to encourage people to do otherwise. It is like visiting your doctor, getting a diagnosis, and then going to your health food store and getting a contrary recommendation from a clerk—then doing what the clerk says! You’re being incredibly stupid—straining out a gnat to swallow a camel. It’s the same mistakes that young earth creationists (or any other crank advocates) engage in: focus hard on a decontextualized fact here and there, ignore expert opinion, and blow off the big picture. Holocaust deniers do it, too. You’re in atrocious company.
—Santi