Is Pfizer’s Vaccine Really Less Effective For Fat People?

I’ve received more than a hundred requests to write about a recent Guardian article with the headline “Pfizer vaccine may be less effective in people with ob*sity, says study” with the subtitle “Healthcare workers with ob*sity found to produce only about half the antibodies healthy people do”

The headline, subtitle, and article that follows are, at best, an example of the stunning scientific illiteracy that exists in mainstream reporting and, at worst an abandonment of journalistic ethics in the pursuit of the clicks that fatphobia always generates. (I’m not linking to the article, giving them additional clicks rewards their bad behavior and I’m not going to do that here.)

Just in summary, “fat people’ and “healthy people” are not two opposite, comparable categories (and “person first language” for fat people is a terrible idea.) Also, the study actually found that older people, cis men and fatter people had similar responses, but all we’re hearing about in this story (and every other one I’ve seen) is fat people. Huh, I wonder why that could be?

The study has not even been peer-reviewed yet, and there is literally no action that should be taken by the public based on its findings, so there is no reason (and certainly no rush) to publish it in a way that increases weight stigma, and possibly decreases fat people’s willingness to be vaccinated.

So the headlines are trash, but what about the actual study?

A content note before I start. The research around this is rife with the use of terms overw*ight and ob*se that were created for the sole purpose of medicalizing and pathologizing fat bodies in ways that are harmful on many levels. I’ll notate them as above as a reminder of that.

Alright, let’s go…

For some background, the study’s own authors explain that

A large clinical trial phase 2/3 with 44,000 people showed that a two-dose regimen of the vaccine BNT162b2, developed by BioNTech and Pfizer, has 95% efficacy in preventing symptomatic COVID-19.

I also want to add that (in a move that actually represents progress in medical weight stigma,) unlike vaccine development in the past, fat people were actually well represented in these trials (comprising 70% of the total subjects) and the vaccine was shown to be equally effective on fat people. (Research on this is available here (look as slides 42 and 43) and here, with a trigger warning on both for fatphobic language.)

To summarize, those were large-scale trials designed to test efficacy, and they showed 95% efficacy in preventing symptomatic COVID-19 including for fat people.

The study that The Guardian is discussing is a small study (248 people, all healthcare workers) whose goal is to look at a specific immune response in vaccinated people, and then compares that response between groups based on factors including age, gender (on a binary only, as is often the case there is a complete lack of trans and nonbinary representation here,) and BMI (which they admit is a “crude measurement” which is just scratching the surface in terms of the issue with using a measurement that has racist origins and fatphobic uses.)

When it comes to study design, this line is of particular interest:

Although the role of neutralizing antibodies to SARS-CoV-2 is under investigation, measurement of serum neutralizing activity has been demonstrated to correlate with protection for other respiratory viruses, such as influenza(3) or respiratory syncytial virus(8) and is commonly accepted to be a functional biomarker of in
vivo disease protection(9).

Which is to say that they aren’t sure if/how/to what degree the immune response that they are studying actually impacts COVID immunity.

So anyway, they administered both recommended doses of the vaccine, and then tested for specific antibody levels seven days after the booster dose.

As I mentioned before, their results found that cis men, older people, and fatter people all developed fewer antibodies than cis women, younger people, and thinner people (though there was a lot of overlap in the actual ranges.) And, just to reiterate, I can’t help but notice that all of the headlines I see when I google this ONLY talk about fat people.

Now, I want to be clear that it’s important that research like this happens. It is absolutely possible that different bodies have different immune responses and thus require different vaccine protocols (the “supershot” flu vaccine being created for older people whose response to the typical flu vaccine isn’t as robust is a good example of this. The fact that fat people also don’t respond as well to flu vaccine but that there is no alternate protocol developed for fat people is a good example of fatphobia in medicine, but that’s a topic for a different post.)

What we cannot scientifically and should not ethically do, is blame fat bodies for this issue, and what we should not do from a place of journalistic ethics is report on small, pilot studies as if they provide information that is immediately useful and relevant to the general public.

It’s also important to point out that, if the antibodies that they are testing do in fact provide immunity, the study authors have no idea what level of antibodies would be required to confer that immunity, so they don’t know if older people, cis men and fat people are producing enough antibodies or not, which is to say that the fact that they produce less may not have any impact on actual immunity.

What we do know is that in large-scale trials that included fat people, the Pfizer Vaccine was shown to be “95% effective in preventing symptomatic COVID-19”

I cannot stress enough that absolutely no conclusions can be drawn from the study that the Guardian and other outlets are “reporting” on. More research is needed and until it is completed this type of “reporting” is dangerous and inappropriate.

I wanted to check my work, so I reached out to Deb Burgard, PhD, who is a psychologist and expert in weight science, who added the following (and found the links to the original Pfizer data which were a much more direct, and less fatphobic, than the source that I was originally using)

I really just have one question, which is whether the use of the measured antibodies from the swab test on day 7 should be an operational definition of ability to fight the virus, especially when we have other studies that did not show a difference between BMI groups in the actual relevant outcomes like getting sick or being hospitalized or dying.

She also pointed other issues with the study:

There are other factors that can correlate with BMI among hospital workers – like Socioeconomic status (fewer fat doctors than nurses, fewer fat RNs than LVNs) – you have all kinds of possible confounding variables. It is even possible to posit that something about the physiology of thin and fat people could be different so that different snapshots might emerge on day 7 but it doesn’t make a difference in how people do after actual exposure. 

She concluded

I understand their wanting to know if they should tweak the dosages for higher or lower BMI but there really isn’t a shortcut to doing the science and seeing what happens in the real world.

So what does this study mean? To researchers – that more studies are necessary. To the general public – not a damn thing. It’s been recommended that everyone get vaccinated and then continue to take precautions, and that recommendation is unchanged for men, older people, and fat people regardless of the findings of this study.

What do all these headlines mean? My guess is they means that fatphobia sells and the Guardian, and other outlets that published similar headlines, are hoping that we are buying.


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5 thoughts on “Is Pfizer’s Vaccine Really Less Effective For Fat People?

  1. That kind of fear-mongering is why I have not followed any news links about the vaccines and have tried to find information from actual research papers and doctors.

    All I want is a vaccine that keeps people from getting really sick and/or dying of covid, and I want everyone to have it as soon as possible.

    Fatphobia was rampant today – WHO announced it is anti-obesity day or some such. I saw a couple headlines about the dangers/addictiveness/horrors of fast food.

    I’m going to watch a movie and snuggle with my cat.

  2. After getting my first dose of the Pfizer vaccine this week I’ve experienced not even a little soreness in my arm, which makes me wonder if the needle had been long enough to get the vaccination into my muscle tissue. I wouldn’t be shocked if too-short needles could cause an overall drop in efficacy among larger people.

    1. Hi Judy, I’m so glad that you got vaccinated. This can definitely be an issue (and could have impacted the findings of this study) and Public Health England (which is the only COVID-specific rec I could find on this) is recommending a 38mm needle for fat people, rather than the standard 25mm.
      I do want to point out that a little more than half of those in the trials didn’t experience any side effects at all they were still 95% protected, and 70% of the study population was fat and they were also 95% protected.

  3. I am so grateful for this resource of information and collaboration!
    I just got my first shot on Thursday and have heard longer needles might be a thing. I had planned on asking about it when I went to the clinic, panicked about having an awkward conversation about being fat and needing accommodations, and just smiled meekly and took the shot.
    I had not heard/read this info that the trials for Pfizer were so diverse. It’s such a relief!
    Thank you for doing such thorough research!

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