Do Higher-Weight People Need Longer Needles for Vaccines?

Fat People and Vaccines - Part 2

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This is the second of a two-part series about vaccines, fat* people, and weight stigma. You can find part one here.

Let’s start with some vaccine basics. Many vaccines, like those for COVID-19, are intramuscular, which means that they are intended to be injected directly into muscle. Muscle tissue has a good blood supply and contains immune cells which recognize the antigen from the virus (or, as in the case of those like the COVID vaccine, the antigen blueprint) and injecting into the muscle starts a chain reaction that produces the desired immune response.

These vaccines are typically not as effective if they are injected into subcutaneous fat tissue. Fat tissue has less blood supply which slows the movement of the antigen through the body, and the wait time can also allow enzymes in the fat tissue to denature the antigen, Also due to lower blood supply, the vaccine stays in the tissue longer which can increase adverse effects including inflammation and irritation.

As you may have already known (or guessed!) this impacts fat people. Intramuscular vaccines are most commonly injected into the deltoid muscle in the upper arm. A layer of subcutaneous fat sits on top of that muscle, the thickness of which can vary among individuals, and tends to be thicker in cis women and also for fatter people of all genders. In order to optimally vaccinate someone, the combination of vaccination technique (whether the skin is pinched or pressed flat) and needle length must be adequate to penetrate the fat layer and reach into the muscle.

Since this is so obvious, you might imagine that it was a primary concern in the research around needle length. If so, you would be wrong. In 1997 a study used ultrasound, height, weight, and mid-deltoid arm thickness “To measure deltoid fat pad thickness and determine the optimal needle length for deltoid intramuscular immunization in healthy adults.”

And by “healthy,” they also meant “not very fat.” For example they studied cis men only up to 260 pounds and failed to have any trans or nonbinary representation. They concluded that a 25mm (1 inch) needle would be sufficient across the weights they studied. They did also note that “[cis] women greater than 90 kg would require a 38mm (1.5-in) needle to ensure intramuscular administration.” (No word on heavier men, or trans and nonbinary folks though, and obviously there are many variables to this including individual body composition, fat distribution, health conditions that impact fat distribution etc.)

So they studied something that is, pretty obviously, more applicable to fatter people and they chose to excluded fatter people. If you want to find more weight stigma, you don’t have to look very far. Since at least 1997 we have been aware that 25mm needles cause issues with vaccine efficacy for higher-weight people, but in many healthcare facilities and vaccination operations, the standard needle has still been 25mm, and fat bodies have then been frequently blamed for a lack of efficacy.

This is what I’m talking about when I discuss the ways that fat people are harmed because we are left out of research, and then our bodies get blamed for that harm. (Health writer Frederik Joelving wrote about this needle length issue for Reuters in 2010 and he saved his compassion not for the fat people being harmed, but rather for 25mm needles, which he lamented were a “casualty” of fat people existing.)

So the current situation is this: Information about needle length that can be life-saving has been around for at least 24 years, and application of that information to prevent harm to fat people is still patchy, at best.

As COVID-19 vaccine rollout began last year, the CDC put out guidelines on this. One thing to note is that the last category lists a minimum weight of 260lbs for cis men and 200lbs for cis women (again, no trans or nonbinary representation here, and many of these are weights of people who were not actually included in the initial studies,) and then just says “and up.” I cannot find research to back up the idea that a 1.5 in needle will work optimally for people of any weight over the minimums listed. Which means that, once again, the lack of inclusion in research poses the most harm to the highest weight people, who then typically get the most blame and shame for the harms created.

Even with these CDC guidelines, as vaccines rolled out during the pandemic I heard from some healthcare practitioners who were administering the vaccine and were told to take their best guess as to whether the patient should get a longer needle, but not talk about it with the  patient.

I heard from patients who requested longer needles but were told they weren’t available which, in the early days of the vaccine, put them in the position of getting a possibly suboptimal vaccination or delaying vaccination while they tried to get another appointment somewhere else (if another location was available.) Some sites (including, we were told, the FEMA site where my partner and I got our first two shots) used 38mm needles for everyone.

I just heard from a fat woman who was getting her COVID booster and called ahead to confirm that they had the 38mm needles, and then re-confirmed with the nurse giving the shot. When the nurse came back with the supplies, the needle didn’t look long enough, so the patient asked her if it was the 38mm. The nurse responded “I like to use the shorter needle because it’s less scary.” I would argue that it’s not less scary than getting COVID-19, or agreeing to a patient’s request and then blatantly, purposefully ignoring it.

Here again we see an example of how healthcare inequalities negative impact fat people’s health (and, again, fat bodies get blamed.) Thinner people can typically feel free to simply arrive at a vaccination site and know that they will be given the vaccine with a needle length that has bene shown to be optimal through careful study. Fat people have to find a way to call ahead to make sure that the facility has bothered to stock the needles of the length that we’ve known for almost a quarter century are necessary for fatter people, then have to trust healthcare practitioners that they will, in fact, use the needle length that was discussed, or bring our own rulers to check.

Vaccinations save lives, and even with a too-short needle getting vaccinated offers more protection than not being vaccinated. Still, the healthcare system needs to care enough about the lives of fat people to include us in research, stock the necessary supplies, and get it right every time.

I’ve created printable cards and scripting to help higher-weight people access the proper length vaccine needle. You can find them here.

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More Research

For a full bank of research, check out https://haeshealthsheets.com/resources/

*Note on language: I use “fat” as a neutral descriptor as used by the fat activist community, I use “ob*se” and “overw*ight” to acknowledge that these are terms that were created to medicalize and pathologize fat bodies, with roots in racism and specifically anti-Blackness. Please read Sabrina Strings: Fearing the Black Body – the Racial Origins of Fat Phobia and Da’Shaun Harrisons Belly of the Beast: The Politics of Anti-Fatness as Anti-Blackness for more on this.