Right or left arm? It may actually matters where you get your COVID booster, study shows

Originally published at: Right or left arm? It may actually matters where you get your COVID booster, study shows | Boing Boing


Apologies for nick-pickery, but the post title is somewhat misdirecting relative to the study. The study was about whether using the same arm for subsequent vaccinations makes a difference relative to alternating arms, not particularly “left” or “right” arms. sorry to be a twit, blame m’self …sorta into all things symmetry; that is, posting a cartoon of a DNA molecule incorrectly twisting to the left sort’ve makes me itchy [wink]. Interesting post nonetheless!


I always take shots in the left arm. the right cost too much to put all those tattoos on to be poking non-decorative holes in it.


I always default to left arm in case the arm gets sore at least it’s not my dominant arm/hand.


i’ve alternated. for no good reason other than to get the whole body workout. i’ve also changed up the manufacturer. i’m still alive, so… success?

( when i did get covid last year, it knocked me down pretty bad. so maybe that’s telling. a/b experiments would be easier with time travel )


Or somehow have a quantum body. You can then simultaneously get shots in both arms (and in neither).


i feel like people already question my existence. is he alive, or is he dead? who can say. maybe i should get out more…

I’ve defaulted to my dominant (right) arm, because I read that soreness is less/passes quicker the more you use the muscle after the shot. With my limited testing that seems about right.

(Also I sleep on my left side, and soreness on my sleeping arm seems more annoying to me, so I actually rate that above anything else.)


Here they always ask your non-dominant arm and the assumption is that’s where it’s going. The arm hurts every time so that’s fair enough.




I always let the person with the needle decide. I always tell them whatever is easiest for you. Same with blood work.

So unless someone wrote it down in my permanent record we’ll never know.

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Having a doctor take your bloods is like third choice. After nurse, after phlebotomist. You won’t even notice a phlebotomist take your blood. Experts being experts is a real source of joy for me. Like me staring at chefs just being so goood at their shit.


I’ve yet to have a smooth experience with blood draws in 39 years of life. The last one i had to stop them from repeatedly poking at my arms and told them to use the vein on the top of my hand, it was painful but they found it in one go.

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it was a long time before i realized some people have veins that are naturally more visible and closer to the skin surface and some people’s are naturally more interior ( i’m sure there’s a term for it ) - one is definitely easier for phlebotomists than the other.

nothing like someone digging around to find a vein. shiver

( i guess covid vaccine goes in your muscle though )

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Someone close to me who was born with severe cerebral palsy, and has had numerous significant medical issues since birth, had one arm that worked somewhat better than the other. She could use it to pinch a glass or soda can to her chest and take a drink from a straw, for example.

That’s the arm the nurse chose to inject the first dose of the COVID vaccine, probably because of the discomfort or recovery factors.

And of all the incredibly unlucky people in the world, she’s the one who drew the very shortest straw and had a severe reaction to the vaccine. It paralyzed her better arm, which has been useless for nearly three years now.

So I get all my vaccines in my non-dominant arm. I don’t care about pain or stiffness if partial paralysis is a potential side effect. Even though it’s highly unlikely, it’s a simple, no-cost, no-effort step I can take to reduce the risk of a terrible outcome.


I think this study is a great example of the difference between statistical and clinical significance.

Yes some of these metrics have some measureable deviation by a p-value < 0.05. But the effect sizes (magnitude of the effect) are tiny.

So while this is an interesting observation from a biology perspective I would be suprised to see any changes in clinical practice from this initial study. Basically don’t be concerned about the efficacy of your current vaccines and arm preferences yet.

And to get a bit technical… There is no mention of multiple testing correction which is suprising for a study that evaluated soo many measures. (This is a method we use to account for random chance findings when you repeat something a lot of times) I’m genuinely suprised that didn’t come up in the review process and will have to read more critically later. It’s usually the first thing I call out when I review a paper like this…

This also feels like a good time to drag out one of my favourite papers on statistics and what a p-value isn’t https://www.tandfonline.com/doi/full/10.1080/00031305.2016.1154108

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My first thought, without having read the paper, was that 303 people is a relatively small dataset to be drawing this conclusion unless it was a large effect size. My second thought was that was that there was no a priori mechanism specified to explain it. Why should two shots in one arm be better than a shot in both arms? Again, maybe that was explained in the paper itself, but if not then this sounds a lot like a fishing expedition (or “hypothesis generation” to be polite).

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Yeah, my long-time fear of needles came from an experience when I was seven years old. I was in the hospital to have my tonsils removed. They had me come in the night before; they sent an intern in to get a blood sample, and he could not find the vein to save his life. He kept wiggling the needle around (after sticking it into my arm, of course) trying to get it to catch on the vein. Brrrr. :scream:

I had a phlebotomist tell me that I was a “tough stick” once; she said that my veins are deep, and they sort of “roll” when the needle touches them. Since then, I relate that story whenever I encounter a new phlebotomist.

similar story only with an iv drip. if at first you don’t succeed just dig around and maybe you’ll get lucky. :scream_cat:

i guess i’m lucky it didn’t leave me with a fear of needles ( i was in my teens so maybe that helped. ) jersey hospitals however… no thank you

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