Wed 2021-Aug-18

COVID-19 Vaccines and Alzheimers: Analyzing the Myth

Tagged: COVID / JournalClub / MathInTheNews / PharmaAndBiotech / Politics / SomebodyAskedMe

Somebody asked me about whether the COVID-19 vaccines prevented Alzheimers. Wait, what?

That’s not the way the conspiracy theories usually work?

Usually, the conspiratorial thinking around vaccines hints darkly, without real evidence, that some nefarious thing will happen to you if you get vaccinated. Like, for example, give you infertility or give you Alzheimers.

So it’s a bit… unusual to hear a rumor that a COVID-19 vaccine will prevent Alzheimer’s, i.e., do something good for you. (Beyond, y’know, not dying of COVID-19, which is definitely a good thing but somehow always gets left out.)

So while I’m very, very tired of knucklehead conspiracy thinking, this looks like something diffferent.

Where do we start?

WSJ: Could COVID-19 vaccines prevent Alzheimers? So it was with something of a sinking heart I learned from my source that he read it “somewhere in the Wall Street Journal”. Now, I’m a lefty, socialisty, intellectual type who thinks you should probably never take medical advice from the WSJ. And certainly not from the OpEd page, which is where our source is. (Needless to say: don’t take any advice on any subject from the dreaded Editorial page, in fact don’t even read it. Too many cognitive hazards from the right-wing propaganda.)

Still, with a sigh, we found the article in question. [1] It’s of course paywalled, because WSJ. But the first 5 paragraphs give us a general idea:

  • First, the author is on board with COVID-19 vaccines being a generally great idea:

    Covid vaccines enormously reduce the risk of death and hospitalization in those who have been infected by the novel coronavirus.

  • But then, they form the relation to COVID-19 always in question form. This is a bad sign, generally indicating a reporter who doesn’t want to get caught on the wrong end of a fact-check:

    But could they also help protect seniors against dementia and Alzheimer’s disease? There’s reason to hope so.

CMAJ: TDaP, polio, and flu vaccines associated with lower Alzheimers

  • They explore some studies on the incidence of Alzheimers among people who took or did not take other vaccines, notably TDaP, polio, and flu. [2] Now, I’m not familiar with that paper from way back in 2001, and nobody’s made much noise about vaccinations as prophylactic against Alzheimers. Still, it sort of makes sense: people who get regularly vaccinated probably watch their health, listen to their doctors, and don’t come down with horrible diseases that probably have brain effects. It’s easy to believe a link to general health behavior, but hard to believe a specific link to vaccines.
  • If you find one study that says something unusual, nobody much cares. Can you find multiple studies that form a pattern?
    Jnl Gerontology: TDaP vaccines and lower Alzheimers
  • Our intrepid WSJ OpEd writer found one other study, from earlier this year. [3] This study involved only the TDaP vaccine, but found a hazard ratio between the vaccinated and unvaccinated of 0.58 (95% CL: 0.54 – 0.63). That’s quite significant! They go on to assert, but show no data, that other vacccines do something similar. (The WSJ OpEd article misquotes the hazard ratio as though it is a percent, which does not really inspire confidence in me.)

Notice something in all that evidence? There’s no relation to COVID-19 or COVID-19 vaccines at all! It’s just making a claim of guilt by association: those other vaccines help (slightly) to prevent Alzheimers, and COVID-19 vaccines are also vaccines, so maybe they help too?

This is skating on ice so thin it might as well be surface tension. I mean: yeah, maybe. But this is not evidence.

Casting a wider net

Ok, if we want actual evidence, we’ll have to cast a wider net.

Alzheimers Association: COVID-19 Advice for Caregivers and Patients The first stop for anyone living with, or caring for someone living with Alzheimers should be the Alzheimers Association. They’re highly reputable, and full of the latest, best medical advice. They have, of course, a page about COVID-19 vaccination for caregivers and recipients. [4] It’s full of good, compassionate advice, but it mostly comes down to: get vaccinated. Both caregivers and patients. There are, of course, some thorny problems about consent with Alzheimers patients, so a medical power of attorney is a useful thing.

But nothing about prevention by the vaccine, just that the vaccine prevents COVID-19. Which is, after all, the point of the vaccine!

UT Health San Antonio: PET scan & gene evidence of COVID-19 and Alzheimer's similarity There is, however, intriguing evidence in the other direction: getting COVID-19 may set the stage for Alzheimers! NPR reports on some (apparently as-yet-unpublished?) evidence from UT Health San Antonio. [5] Their dataset was PET scans of people before and after COVID-19. (I wonder how that happened? How do you get IRB permission to PET scan people on the chance they might later get COVID-19?) The images post-COVID-19 apparently resemble Alzheimers patients (though the NPR report doesn’t say why) and “some of the genes” that predispose sensitivity to COVID-19 are also sensitivity markers for Alzheimers (though the NPR report doesn’t say which genes).

So… that’s maddeningly vague. But given the havoc COVID-19 induces, even in the brain, it’s totally believable that some pre-Alzheimers phenotype might happen. So in that case, COVID-19 vaccines would prevent Alzheimers… by preventing COVID-19 itself!

Reuters Fact Check: no evidence vaccines cause Alzheimers Finally, why isn’t there a conspiracy theory saying the vaccines cause Alzheimers? That’s the way it’s usually supposed to go. Fortunately, Reuters has a “Fact Check” article ready to go. [6] They reassure the timid that: the Pfizer vaccine does not cause prion diseases like Creutzfeldt Jakob disease, it does not cause Alzheimers, and it does not cause Lou Gehrig’s disease (ALS). The rumor is traced to the conservative “news” site Gateway Pundit (to which I refuse to link). It apparently got published in a low-quality journal, because accidents like that happen. The author, J Bart Classen, has a history of attempting to publish inflammatory articles skeptical of all vaccines. Experts consulted by Reuters pronounced his proposed mechanism nonsensical.

So… there is a conspiracy theory that COVID-19 vaccines cause Alzheimers. Given its origin in the conservative web, it is predictably nonsensical.

The Weekend Conclusion

  • There’s no particular evidence that the COVID-19 vaccine prevents Alzheimers. Some other vaccines (TDaP, polio, flu) have been shown to do that somewhat, but the only link to the COVID-19 vaccine is that they’re all vaccines.
  • While there is a conspiracy theory by some right-wing anti-vax crank that the COVID-19 vaccine causes Alzheimer’s, it is nonsense and you should ignore it.
  • There is mild evidence that COVID-19 causes some brain changes that superficially resemble Alzheimers. So you can – somewhat awkwardly – claim that COVID-19 vaccines prevent Alzheimers by preventing COVID-19 itself.

The point seems to be: don’t worry about Alzheimers; get vaccinated; if there’s a preventive effect that’s fine, but it’s more important to prevent getting COVID-19.

Notes & References

1: A Finley, “Could the Covid Vaccine (and Others) Prevent Alzheimer’s?”, Wall Street Journal Opinion/Commentary page, 2021-Aug-05. NB: The article as a whole is paywalled, beyond the first 5 paragraphs.

2: P Verreault, et al., “Past exposure to vaccines and subsequent risk of Alzheimer’s disease”, Canadian Medical Assn Jnl, 167:1-13, 2002-Jul-09.

3: J Scherrer, et al., “Lower Risk for Dementia Following Adult Tetanus, Diphtheria, and Pertussis (Tdap) Vaccination”, Jnl Gerontology Series A: BIol Sci & Med Sci, 2021-Apr-16.

4: Alzheimers Association, “COVID-19 Vaccine: Answers for Dementia Caregivers and People Living with Alzheimer’s”, Alzheimer’s Association, retrieved 2021-Aug-18.

5: J Hamilton, “Doctors Worry That Memory Problems After COVID-19 May Set The Stage For Alzheimer’s”, NPR, 2021-Jul-26.

6: Reuters Fact Check, “Fact Check-No evidence that Pfizer’s COVID-19 vaccine causes Alzheimer’s disease”, Reuters, 2021-May-21.

Published Wed 2021-Aug-18

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