Can a mild Covid breakthrough case lead to cognitive impairment?
August 10, 2021 12:08 PM   Subscribe

Is there any info yet on breakthrough cases in vaccinated people leading to cognitive deficiencies?

We know that (1) breakthrough cases in vaccinated people can lead to long-term symptoms.

And we know that (2) even mild cases of Covid can lead to cognitive impairment.

To me this suggests that the kind of asymptomatic or mildly symptomatic cases we've come to expect from breakthrough cases could nonetheless lead to cognitive deficiencies. But have any doctors, public health officials, or other reputable sources addressed this yet?

I understand that when asking about long-term effects, it might just be too soon to know. But that makes me feel like we're really rolling the dice with our future. My wife goes back to teaching in person in a month. She's 38 and double vaxxed.
posted by Beardman to Health & Fitness (11 answers total) 10 users marked this as a favorite
I suspect it would be hard to differentiate between cognitive impairment caused by the extreme stresses of the times, and cognitive impairment caused by Covid.

There would be so many factors that could affect any such study. Medical and psychiatric history, employment, financial status, social status, marital status, etc etc

I was part of a large NIH funded study over the last 16 months, I submitted blood and answered lots of questionnaires and on-phone questions. Anyway they concluded that for every person who was tested positive with Covid there were five who were asymptomatic and didn't get tested. So it's been way more widespread than we knew, and any study of cognitive impairment would have to take that into account.
posted by mareli at 12:41 PM on August 10, 2021 [1 favorite]

As a non-subscriber I can’t click though to read your WaPo article— is it addressing this study here on the significant post-infection gray matter loss in even asymptomatic cases of COVID? Per this epidemiologist author, there’s no way to know yet if this sort of thing necessarily leads to actual persistent cognitive deficits.
posted by blue suede stockings at 12:47 PM on August 10, 2021

Not an article on cognitive deficiencies but on Long COVID (which can include such things): Can You Get Long COVID if You’re Vaccinated?
posted by thebots at 2:13 PM on August 10, 2021 [1 favorite]

I suspect it would be hard to differentiate between cognitive impairment caused by the extreme stresses of the times, and cognitive impairment caused by Covid.

No, there's a difference. I wasn't just a little slower, I was unable to process multiple sensory inputs enough to read subtitles and still be able to follow what was going on in the movie. I had to stop listening to music more complex than a person singing and playing guitar with themselves for several months, and I'm a professional musician. Like I know everyone's had a shit year, but brain fog from COVID is an entirely different, stinkier, pile of shit.
posted by Gygesringtone at 2:23 PM on August 10, 2021 [37 favorites]

Best answer: I don't have sources for you on other research or statements from officials, but I want to take a little time to break down that particular study as an example of how difficult it can be to read and understand scientific studies, and what you might consider when thinking critically about them.

Here is the study in question (which is not a peer-reviewed article, just presented at a conference).

Couple things to note. One, it doesn't actually say anywhere that people who had COVID-19 had statistically more cognitive impairment than people who didn't have COVID-19. There is not a reported test showing that people with COVID-19 were significantly more likely to have cognitive impairment.

Second, what it says about mild COVID-19 in specific is:
Severity of cognitive impairment was significantly correlated with severity of olfactory dysfunction (χ2 = 13.82; p= 0.003) but not severity of acute COVID-19.
Olfactory dysfunction is measured as part of the test; this is referring to olfactory dysfunction at the time of testing. This is saying that if you continue to have olfactory dysfunction even after recovering from COVID-19, you may have cognitive impairment. This is not new information; cognitive impairment and olfactory dysfunction have been previously linked.

So, first of all, there's no evidence that asymptomatic cases would experience cognitive decline. It's possible, that if you had a breakthrough case and all of your COVID-19 symptoms were mild, but you had severe loss of smell that persisted for months, that it could lead to cognitive impairment (based on this data). But we definitely don't have data on how likely that particular presentation of symptoms would be.

Also, the sample only included people over 60 years old. I can't tell from the abstract how they controlled for age-related olfactory dysfunction. We know that olfactory dysfunction occurs as a part of aging, and that it predicts cognitive impairment in the normal aging process. It's possible that some of the people with persistent olfactory dysfunction were experiencing normal age-related loss of smell, which is related to cognitive impairment regardless of COVID-19. Since this abstract does not report on any comparisons to the control group, it's impossible to draw conclusions about this.

Finally, a statistically significant difference is not equivalent to a clinically significant difference. Take this with a grain of salt because I'm not entirely sure what they're doing with their graph (labels, people!), but it looks like people categorized as having "multiple domain impairments" often varied from the mean by less than one standard deviation. On cognitive measures, anything less than one standard deviation away from the mean still falls in the average range. It may be the lower end of average (though most measures go: 1 SD = average, 2 SD = low average, 3 SD = below average,=) but it's not in the impaired range.

This means that even if they experienced cognitive impairment, it was so little that we would not qualitatively label it any differently. It's been a while since I administered a Wechsler Memory Scale (one of their measures), but I'm pretty sure the scale ranges from 0-25. A difference of 2.2 (Logical Memory Long Term Recall's difference) is statistically noticeable, but would be unlikely to make a discernible difference on your day-to-day life.

Does this mean asymptomatic/mild COVID-19 definitely doesn't cause long-term cognitive impairment such that it could significantly impact people's lives? No, but the data that article is pulling from doesn't support that as a broad, unqualified statement regarding COVID-19 risk.

Hope that helps. Wish we knew more. Let me know if I need to clarify anything.
posted by brook horse at 3:43 PM on August 10, 2021 [23 favorites]

You're not going to find much that is definitive on this, because there is so little research. But clearly, cognitive impairment (many people call it brain fog) is a symptom that people experience after a COVID infection. It is also a symptom of myalgic encephalomyelitis, aka chronic fatigue syndrome, which has a lot of similarities to long COVID and is often post-viral as well (in fact, many people with long COVID that lasts for more than 6 months would be diagnosed with ME/CFS based on diagnostic criteria). SARS-CoV-1, MERS and many other viral infections have resulted in ME/CFS for those infected, so this is not at all without precedence.

I don't think there's much doubt at this point that even mild COVID can have long-term consequences that last for many months. Nor is there any particular evidence that vaccines prevent these types of long-term consequences for those who do get infected (obviously, vaccines do help prevent long-term issues from severe COVID by preventing severe COVID). So it does seem reasonable to assume that vaccinated people who are infected could suffer from long COVID symptoms (of which cognitive impairment is one, but certainly not the only or the most devastating).

The real question is what is the risk and that's not a question that can be easily answered. My own interpretation of the data is that we're headed for a significantly more dangerous fall than is generally anticipated. In general, I think we are badly underestimating the long term consequences of COVID infections, by ignoring long COVID / ME/CFS in our decisions to reduce or eliminate social distancing, masking, and other public health measures. By focusing on hospitalizations and deaths, we discount these long-term impacts and make decisions that will have negative consequences for many.
posted by ssg at 4:32 PM on August 10, 2021 [4 favorites]

We know it's possible to get Long COVID from breakthrough infections, and a major symptom of Long COVID (even in non-hospitalized, non-respiratory cases) is cognitive dysfunction, so this seems very possible.

As someone who had it, I will also say it's pretty debilitating and not worth any risk. I would do anything to get my brain back. I'm a young person and haven't been able to go back to work in over a year.
posted by todolos at 6:39 AM on August 11, 2021 [4 favorites]

New England Journal of Medicine study:

“Among 1497 fully vaccinated health care workers for whom RT-PCR data were available, 39 SARS-CoV-2 breakthrough infections were documented.”

That’s 2%.

“Most breakthrough cases were mild or asymptomatic, although 19% had persistent symptoms (>6 weeks)”

That long haul percentage is .5% of all vaccinated healthcare workers.

The percentages aren’t meant to minimize risk. Healthcare workers might possibly be more protected than general public at this point so it’s hard to know exactly how significant the 2% number is.

We just don’t know fully on long covid with vaccines in the mix, either. We especially don’t seem to have full answers on cognitive impairment. But studies consistently show the vaccines are working with breakthrough infection severity and incidence. Is there still risk, however? Of course, we just need more studies.
posted by glaucon at 11:31 AM on August 11, 2021

Here’s some more research on Long Covid from Nature and published two days ago.

More than 50 long-term effects of COVID-19: a systematic review and meta-analysis

And a graph from the article, which shows many different patient experiences and percentages of incidence.
posted by glaucon at 11:39 AM on August 11, 2021

“Among 1497 fully vaccinated health care workers for whom RT-PCR data were available, 39 SARS-CoV-2 breakthrough infections were documented.”

That’s 2%.

Important caveat, given what we are learning day to day about the waning effectiveness of vaccinations over time and the increased breakthrough potential of the delta variant: paper is very clear that these cases were from earlier this year, and the alpha variant.

Just released from Mayo:
“In a study of more than 50,000 patients in the Mayo Clinic Health System, researchers found the effectiveness of Moderna's vaccine against infection had dropped to 76% in July - when the Delta variant was predominant - from 86% in early 2021. Over the same period, the effectiveness of the Pfizer/BioNTech vaccine had fallen to 42% from 76%, researchers said.”
posted by blue suede stockings at 12:19 PM on August 11, 2021 [3 favorites]

Thank you, blue suede stockings, for the very important caveat and new data.

I heard on NPR or The Daily last week or week prior that the CDC wasn’t even prepared to study breakthrough infections because they were considered not highly likely. I hope we start seeing better research and data soon. We need it.
posted by glaucon at 1:47 PM on August 11, 2021

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