Adventures in ill-advised medical contrarianism

>> Monday, November 09, 2009

Over at Science-Based Medicine, Mark Crislip offers a long, detailed and highly-informed critique of this cover story in The Atlantic that speculates (sloppily) about the efficacy and safety of the vaccine for H1N1/09. Unlike Crislip, I'm not an infectious disease doctor and I don't intent to play one in the blogosphere, but this is an issue that gets me torqued for all sorts of reasons, so I'll offer a few thoughts of my own.

The problems in the article are numerous, but its central flaws stem directly from the authors' aggressively contrarian reading of the data on seasonal flu vaccination -- dubious interpretations which they proceed to apply inappropriately to the H1N1 vaccine, which has already inspired unprecedented heights of stupidity in recent months. At the bottom of it all, Brownlee and Lenzer seem to believe that because influenza viruses circulate each year in spite of efforts to vaccinate as many people as possible, the seasonal flu vaccine is somehow worthless; and because the seasonal flu vaccine is ineffective, the H1N1 vaccine will prove to be similarly disappointing. The simplest analogy I can come up with is that it's like complaining that because apples don't taste like bananas, you're probably going to hate the pears you just bought.

It's a dubious argument. As Crislip has noted before, the seasonal flu vaccine is "sub-optimal" for a variety of reasons. It's based on highly-educated guesswork about what the possible varieties of influenza A&B will do in a given year; response to the vaccine is hard to predict (in part because of the possibility of mismatch between the virus and the vaccine, and in part because influenza B mutates a lot during flu season, further compounding the mismatch problem); and people generally don't receive the vaccination at high enough rates for effective herd immunity to kick in. Nevertheless, while Brownlee and Lenzer insist that empirical support for vaccination is "thin at best," the collective evidence on flu vaccination strongly suggests that it does provide moderate to high levels of efficacy against the flu, including protections against transmitting the virus to others, which is arguably the most important reason to accept the jab in the first place. Moreover, studies also demonstrate pretty convincingly that when the vaccine matches the strains of influenza that circulate in the general population, efficacy increases dramatically -- evidence that would lend obvious ballast to the idea that we should expect H1N1 vaccine to achieve better results than the seasonal flu vaccine, given that it's derived from the very strain being targeted.

The authors, however -- one of whom has written a well-regarded book on the high cost of medical "overtreatment" -- deliberately ignore the preponderance of evidence suggesting that flu vaccinations provide a safe, inexpensive means of reducing the effects of a virus that we know will kill around 30,000 Americans each year. They brush off that latter fact by pointing that most of those who die from the flu have underlying health problems already; they actually seem to believe this strengthens their case against the seasonal vaccine. In any event, I don't know how someone who writes about the high cost of medical (over)treatment could possibly believe that reducing vaccination levels in the US -- and thus increasing morbidity and mortality -- could possibly be a good thing.

What's worse, the authors raise evidence-free suspicions about the safety of the H1N1 vaccine. Obviously, the actual performance of the vaccine is going to be difficult to measure, given a whole array of factors including the gross overconfidence of its manufacturers, who have delivered less than 20 percent of the promised number of doses to market. But that's an entirely different problem that has nothing to do with (a) the general evidence in support of flu vaccination or (b) the overall safety of the newest vaccine. Brownlee and Lenzer don't elaborate on their suspicions in the article itself. However, in a Q&A that claims to offer "Facts about Swine Flu," the authors warn -- contra the evidence -- that flu vaccines pose a small risk of Guillain-Barre Syndrome (which the authors don't even bother to spell correctly). While there's a plausible hypothetical relationship between GBS and flu vaccines, the data are really inconclusive, and the authors should have said so. Meantime, they sink even deeper into the muck by mentioning squalene and thimerosal, two of the central components of anti-vaccination hysteria. Not only are these two chemicals irrelevant to the origins of GBS, but there's absolutely no causal evidence (much less a convincing hypothesis) that would link autoimmune or neurological disorders with either one. When the authors write that while "many doctors believe [thimerosal] is safe but others believe may be responsible for effects on the brain and nervous system," they are participating in Opinions-of-the-Shape-of-the-Earth-Differ journalism, and they're mainstreaming bullshit pseudoscience. It underscores the problems with the main article, which is is pretty weak tea to begin with.

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