Yesterday, Katja Grace asked, "Why do people avoid vaccination?" I suggested that the answer might be anxiety over getting stabbed with a needle. The main idea is that concern over bodily autonomy is common—indeed, it forms the basis of much of our legal system—but people are perhaps too embarrassed to talk about needle anxiety publicly, so they self-deceive themselves about the real reason why they don't want to get their shots.

Since commenting, I've looked into the issue a little bit, and have decided to share some of my findings.

First, although not strong evidence, it is striking to note that there is a strong relationship between age and vaccine uptake. The young, by and large, are more vaccine hesitant than the old, despite being generally more liberal politically.

This is probably explained to a large degree by the fact that Covid-19 is far more dangerous to older people, and older people are on average more trusting of their physicians.

But here's another fact that could help explain the data: needle anxiety is concentrated in the young, and declines sharply with age. From one meta-analysis, "The results of meta-regression indicated that, for every decade increase in age (years), there was an 8.7% (95% CI: 6.0%, 11.4%) decrease in the prevalence of needle fear (p<0.001)."

The same pattern can be observed across the genders. Women are both more likely to be needle phobic and more likely to be vaccine hesitant. The same meta-analysis concludes, "For needle fear, the pooled female:male prevalence ratio was 1.4 (95% CI: 1.1, 1.8) with  of 89.8% and  of 0.067. For needle phobia, the pooled female:male prevalence ratio was 1.7 (95% CI: 1.3, 2.1) with  of 63.4% and  of 0.038."

By comparison, one study that surveyed a "sample of almost six thousand adult Poles, which was nationally representative in terms of key demographic variables" asked about vaccine hesitancy. Here were their main results,

However, these results may not be robust cross-nationally. In the US, the gender gap looks smaller to me, with FiveThirtyEight even reporting that men were less likely to get the vaccine in June 2021. By September, however, those numbers might have reversed with Pew reporting rates of 74% and 71% having received at least a single dose for adult men and women respectively.

One source just authoritatively states,

Women were significantly more likely to express a desire to delay or reject the Covid-19 vaccine than men were, which is consistent with the existing literature on vaccine hesitancy.

Perhaps the most obvious way of resolving this question is to ask people directly about their needle anxiety and Covid-19 vaccine hesitancy. One study did this and reported,

In total, 3927 (26.2%) screened positive for blood-injection-injury phobia. Individuals screening positive (22.0%) were more likely to report COVID-19 vaccine hesitancy compared to individuals screening negative (11.5%), odds ratio = 2.18, 95% confidence interval (CI) 1.97-2.40, p < 0.001.

They continued,

The population attributable fraction (PAF) indicated that if blood-injection-injury phobia were absent then this may prevent 11.5% of all instances of vaccine hesitancy, AF = 0.11; 95% CI 0.09-0.14, p < 0.001.

However, it is unclear to me whether this is a good estimate of the fraction of vaccine hesitancy that is explained by needle anxiety. As I stated earlier, I think many people may be silent about their needle anxiety for reasons of self-deception, as it's admittedly a flimsy reason to avoid taking a medicine that could save other people's lives.

One hypothesis states that people are hesitant because they are concerned that the vaccines were rushed, or that they don't trust the government. While these explanations almost certainly play some role, and it's one of the primary reasons that people point to when they talk about their vaccine hesitancy, I think we should ultimately be skeptical of this hypothesis on its face.

In general, it take an average of 30 years to develop a vaccine, and yet despite this ample time for testing, history is rife with anti-vaccination sentiment. Political propaganda—such as the idea that Biden and the Democrats are untrustworthy—can only play a limited role in explaining the global statistics, which show that vaccine hesitancy is common in many nations. Trump was more responsible for the vaccine than Biden, yet this fact doesn't seem to impact people's perception of the danger by much. And evidently many people who said they'd "wait and see" before taking the vaccine are still, well, waiting and seeing. This provides a prima facie reason to doubt people's stated motivations.

Only about half of people receive their regular flu vaccines each year, with the same trend by age that we see with Covid-19. Unfortunately, I haven't yet been able to find reliable statistics about hesitancy for other voluntary adult vaccines.

It is true that childhood vaccines reach coverage of over 90% in the United States, but this fact isn't difficult to explain, given that small children don't have a choice in the matter, and it's often a requirement to go to school.

The oral polio vaccine is administered without the use of needles, and therefore could serve as a testbed for this hypothesis. Unfortunately, I didn't find much literature addressing the question directly of how much more people are willing to take an oral vaccine compared to a needle-based one.

That said, given the parsimony of the explanation, the relatively high reported rates of needle anxiety, concentrated in precisely the groups we observe to be vaccine hesitant, the consistency across nations and through history, and the failure of alternative hypotheses to make light of the evidence, I think it makes sense to give the needle anxiety hypothesis a fair degree of credence.

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Is there some way we could use the nasal flu vaccine to test this?

Although I suspect it's hard to test this since once people are "radicalized" against vaccines, they seem to remain anti-vaccine even if their reasons don't make sense in a different context (see: the people who are still worried about ingredients that were removed from vaccines decades ago).

n=1, but I have an immediate squick reaction to needles. Once vaccines were available, I appeared to procrastinate more than the average LWer about getting my shots, and had the same nervous-fear during the run up to getting the shot that I've always had. I forced myself through it because COVID, but I don't think I would have bothered for a lesser virus, especially at my age group.

I have a considerable phobia of needles & blood (to the point of fainting - incidentally, such syncopes are heritable and my dad has zero problem with donating buckets of blood while my mom also faints, so thanks a lot Mom), and I had to force myself to go when eligibility opened up for me. It was hard; I could so easily have stayed home indefinitely. It's not as if I've ever needed my vaccination card for anything or was at any meaningful personal risk, after all.

What I told myself was that the doses are tiny and the needle would be also tiny, and I would hardly notice it; I told my injector that I had a needle phobia and asked to be distracted, and using a topical anesthetic, I didn't even know when he did it. "Hah - that was exactly as easy as I rationally believed, but emotionally could not alieve!" That made the second and third times much easier.

I used to have mild needle anxiety, but it is now greatly reduced (I don't really feel nervous at all until I am about to receive an injection, rather than feeling nervous for roughly the entire day). I think two things have helped:

  1. Just as I am about to receive an injection, I start to focus intensely on something else. Specifically, I recite the sequence 1, 2, 4, 8, ... (doing the multiplication if I don't know the answer by heart) in my head. (I say something to the person giving the injection so they know I won't respond to them.)
  2. I once had to receive several injections over a short period (something like 5 over a few weeks, with 3 on one day) for a trip abroad.

I wonder if there's another even more annoying confounder where pro-vaccine people pretend that they don't have needle anxiety, even though needles are sort of naturally anxiety-inducing. I mention this because I feel like I might be doing this. I do find getting needled pretty uncomfortable! I pretty deliberately control my thoughts about it to avoid thinking about, or reframe, the aversive aspects of hte experience. But if an impressionable member of my tribe asked me about that I would probably downplay the aversion, to some extent, to minimize transmitting discomfort via empathy. Sorry if I've made anyone less comfortable with needles by acknowledging this, here!

Maybe a better way of putting it is, I kind of expect everyone to start out with similar levels of needle anxiety then to not identify with, or to unmake, the anxiety as soon as that would be useful. Causality could legitimately run both ways here.

Sorry if I've made anyone less comfortable with needles by acknowledging this, here!

Those kinds of attempts to "distort" the truth for people for their own good don't actually work well in practice. People tend to notice, as you have, that it's wishful thinking and not actually (completely) true. This means that even though you consciously "believe" that needles are fine and no big deal, that there's still that asterisk there causing anxiety that you try to look away from and try to help others look away from. If you think about what your model is of this hypothetical person becoming less comfortable, I bet you'll find that they already had this asterisk too, and that the thing you're apologizing for isn't for shattering a trust that was pure but rather "making it more difficult to look away from the thing you don't want to see".

The problem isn't the acknowledgement of the strategy, but lack of acknowledgement in the strategy. By attempting to "control" or "downplay" or "reframe" the aversive aspects, the actual impression left on the impressionable is that that needles are so scary that we can't even be honest about it, not even with ourselves (but hey, we can pretend! And if you pretend with me that needles aren't scary then we can also pretend that you're okay!). It's not a complete failure to the extent that you also kinda believe it, but the success sure isn't complete either, and the partial credit for partial success doesn't go to the pretending but to the reasons that cause you to see it as somewhat true.

 

The opposite approach may be counter-intuitive and sometimes a little uncomfortable (e.g. if you still don't like needles yourself), but it works very well. People will look at you like you're crazy if you play up how scary needles are and how much they hurt in front of an impressionable two year old, but If you play up the discomfort to the point where it's hard to tell how serious you are (and enough that it's clear that the answer can't be "entirely"), then the impression left is that it is play, and therefore not too scary to be played with. And that means that when your two year old cries after getting her shot, it's because she couldn't get a second one, which is a much preferable problem to have. When you go out of your way to seek out and highlight the most difficult parts of the experience, it makes it much easier for people to fully trust, because you can be seen to be not-avoiding the difficult parts, and so there's no asterisk left behind. 

If needle anxiety would drive vaccine hesitancy we would assume that vaccine hesitancy does not follow any tribal dynamics of tribes that are not about shared needle anxiety but that contain other political agendas. I don't think that's what we are seeing. 

I do we see people who are generally distrustful of establishment authority to be much more likely to be vaccine-hesitant. 

And evidently many people who said they'd "wait and see" before taking the vaccine are still, well, waiting and seeing.

We do see people getting vaccinated who previously weren't vaccinated in nearly every country. Not as much as we would like but it's inaccurate to present it as nobody has changed.

It could be that people with a fear of needles have allied themselves with other groups and thus taken on their views.

The oral polio vaccine is administered without the use of needles, and therefore could serve as a testbed for this hypothesis. Unfortunately, I didn't find much literature addressing the question directly of how much more people are willing to take an oral vaccine compared to a needle-based one.

There might not be a clean RCT for this but just looking at the history of the Polio vaccine, I seem to find confirmation for this. In the West, the Salk vaccine (which had to be injected) was available since the 1950s but uptake was very slow. Then the Sabin vaccine was developed around 1960, mostly in the USSR with the initial idea from Sabin (a naturalized US citizen), which was an oral vaccine and a much bigger success. This is confounded by the fact that the Sabin vaccine was considered more effective, but on the other hand it also had a slight chance of giving others a real infection because it contained live viruses. So, I don't know how that affected its perceived desirability. Still, I'd consider this slight evidence in favor of oral vaccines being more popular.

The gender gap is further compounded by the menstrual irregularities the vaccine is somewhat likely to cause.

Women talk, and that is hardly a very pleasant experience and it appears common enough for many to notice.

Shouldn't it be easy enough to recruit some people for a study and see whether those who have a needle phobia are the same as those who haven't been vaccinated for COVID?