Tetanus and Medical Innumeracy
My first Community Note on X, and what's wrong with it
Two days ago I went to the doctor to check out a mark on my cheek. During the visit, my doctor heavily pressured me to get a tetanus booster. Instead of offering numbers, she talked to me like a child. I refused the jab, and checked the numbers for myself. According to the CDC, about TWO people per year die of tetanus in the United States.
That’s about one-tenth of the risk of being killed by lightning.
Since I found my experience to be an amusing illustration of doctors’ severe innumeracy, I decided to share it on X. As I write, my tetanus tweet has over a million views… and a Community Note.
As far as I can tell, there is no way to Community Note a Community Note. But the note is flatly wrong. Use of the tetanus vaccine isn’t even close to “near-universal.” Again according to the CDC, only 63% of U.S. adults have followed their recommendation to get a tetanus vaccine every ten years. Since that’s self-reported, the true vaccination rate is probably markedly lower.
Implication: Even the risk of refusing this booster is lower than the risk of dying from a lightning strike. If the self-reported vaccination rate were exactly correct, and the vaccine 100% effective, the probability of an unboosted American adult dying of tetanus would still be about one-fourth the risk of death by lightning.
Nor is herd immunity an issue, because tetanus is not contagious.
Why make an issue of this? Because I oppose innumeracy, and medical innumeracy is one of the most harmful forms thereof. “If it saves one life” is one of the most foolish and dangerous feel-good slogans even voiced.
What, though, is the downside? Like almost everyone, I dislike injections. If I’d gotten the shot, it would have been the worst thing that happened to me all day. You’d have to pay me hundreds of dollars to endure one needless jab. I’ll take the fear and pain of a shot to save a day of statistical life, but not for a couple of extra statistical seconds.
Back in February of 2020, I happily flew to Austin to get my first Covid shot early. Why? Because I knew the numbers. I refused a tetanus booster, again, because I knew the numbers. Or to be more precise, I correctly guessed, then confirmed, the numbers.
In hindsight, I’m not surprised by the angry reaction to my tweet. If a complete stranger says anything negative about vaccines on the Internet, they’re probably crazy anti-vaxxers, not crusaders for numeracy. As an apologist for statistical discrimination and believer in stereotype accuracy, I can’t complain too harshly when they work to my detriment.
That said, (a) getting angry at strangers on the Internet about anything is childish, (b) my tweet made an important point, (c) my evidence was in no way misleading, and (d) I stand by my refusal.
To be clear, Our World in Data convincingly argues that the vaccine has been great globally, especially for kids. All my children got tetanus shots, and I’m glad they did. That doesn’t mean I should get a tetanus booster. When you do math, changing the numbers often changes the right answer.
If my bottom line were just, “Anyone in my shoes should skip their tetanus shot,” I wouldn’t have bothered writing this post. I am eager, however, to take a stand against medical innumeracy. Some doctors work miracles, but almost all doctors fancy themselves poets. And their poetry is godawful safetyism. Whenever doctors urge you to suffer, check the numbers, because they probably won’t.
P.S. It looks like the Community Note was removed, but I’m not sure.
Bryan, thanks for this post. I’m near the end of my career as an internal medicine doctor (first few years) and an anesthesiologist (last three decades). Safety-ism does indeed pervade the profession. It’s a weird combination of paternalism, innumeracy, and some fear of malpractice litigation, though that’s more often used as a post-hoc justification for lazy thinking and for the other silly things we do.
It’s odd; paternalism is officially “out“. We are these days supposed to offer patients our advice, and let them choose (which is often absurd, given the massive knowledge gap), yet we are still paternalistic about the least important stuff. And don’t forget that a number of our specialty societies (looking at you, pediatricians) have decided that their brief is social activism dressed up as “advocating for our patients”.
i’m a little confused here. my understanding is:
- tetanus can be treated even if unvaccinated
- given you are exposed to tetanus and unvaccinated, you will experience uncomfortable/painful symptoms even if you don’t die
- a vaccinated person when exposed to tetanus will not experience symptoms
- given they don’t experience symptoms, the medical system will have no knowledge of this, so those cases are underreported
your argument seems to hinge on the cost of a bad day from vaccination outweighing statistical seconds of lifespan, but doesn’t take into account benefit of preventing symptoms even if you don’t die
presumably you agree there is a mechanism by which tetanus can harm you and that there is a mechanism by which the vaccine prevents that harm. if you’re taking the outside view and looking at some stats, then i think the stats would likely not adequately capture the harms