Having said all that, I do recommend Sharon Brownlee and Jeanne Lenzer's piece in the latest Atlantic, which makes a serious case that the seasonal flu vaccine, and the swine flu vaccine that is modeled after it, may not be as effective as public health officials believe:
When Lisa Jackson, a physician and senior investigator with the Group Health Research Center, in Seattle, began wondering aloud to colleagues if maybe something was amiss with the estimate of 50 percent mortality reduction for people who get flu vaccine, the response she got sounded more like doctrine than science. “People told me, ‘No good can come of [asking] this,’” she says. “‘Potentially a lot of bad could happen’ for me professionally by raising any criticism that might dissuade people from getting vaccinated, because of course, ‘We know that vaccine works.’ This was the prevailing wisdom.”I was surprised to learn that the flu vaccine, as well as antiviral flu drugs like Tamiflu, haven't been subjected to placebo-controlled trials, on the grounds that it would be "unethical" to use dummy shots on populations at risk of the flu. If that were true, wouldn't it always be unethical to do placebo-controlled studies, regardless of the drug or treatment in question? I'm not a public health expert, but it seems bizarre to draw such a line around just the flu vaccine.
Nonetheless, in 2004, Jackson and three colleagues set out to determine whether the mortality difference between the vaccinated and the unvaccinated might be caused by a phenomenon known as the “healthy user effect.” They hypothesized that on average, people who get vaccinated are simply healthier than those who don’t, and thus less liable to die over the short term. People who don’t get vaccinated may be bedridden or otherwise too sick to go get a shot. They may also be more likely to succumb to flu or any other illness, because they are generally older and sicker. To test their thesis, Jackson and her colleagues combed through eight years of medical data on more than 72,000 people 65 and older. They looked at who got flu shots and who didn’t. Then they examined which group’s members were more likely to die of any cause when it was not flu season.
Jackson’s findings showed that outside of flu season, the baseline risk of death among people who did not get vaccinated was approximately 60 percent higher than among those who did, lending support to the hypothesis that on average, healthy people chose to get the vaccine, while the “frail elderly” didn’t or couldn’t. In fact, the healthy-user effect explained the entire benefit that other researchers were attributing to flu vaccine, suggesting that the vaccine itself might not reduce mortality at all.
On the other hand, even after having read Brownlee and Lenzer's article and coming away fairly convinced of its main argument, I still plan to get the seasonal flu vaccine, and the swine flu vaccine if it becomes available to me. And why not? At the least, it does me no harm, and may well do much good. But the more effective things I could do to avoid getting or spreading the flu -- e.g., hand-washing and so-called social distancing from places where flu outbreaks are occurring -- aren't being promoted by the government. Fortunately, the current swine flu pandemic appears to be milder than had been feared; but if a more virulent strain comes along, this over-reliance on vaccination could make things worse for us than would be necessary.
UPDATE: A commenter on Facebook informs me that the flu vaccine and Tamiflu have been subjected to placebo-controlled trials, as all drugs are; rather the controversy revolves around whether it would be proper to do a large-scale study to answer the question of whether they're effective for the populations that are at highest risk for the flu. Since they have been shown to work, at least in some cases, there could be ethical problems in giving a placebo to someone instead of a drug with at least some proven effectiveness. If there were no difference whatsoever in performance between the flu vaccine and a placebo, that would be one thing; but if there's at least some chance that the flu vaccine is more effective, then doing a placebo-controlled trial now could be morally problematic. I apologize for the error.
Even so, I think the question going forward is less about the science behind the flu vaccine and more about the policy response of dealing with flu pandemics. While the efficacy of the flu vaccine may be in question, it does have the advantage of being relatively non-intrusive -- just tell people to get vaccinated, and all is well. Other methods, like social distancing, may be more effective, but they entail the government getting much more involved in how people conduct their daily routines, and could even set off a public panic. So it's a tricky problem in either case.