I'm not a health expert, just trying to understand possible long-term side effects of the vaccine, so if my terminology and thinking is off, feel free to correct.

The prominent vaccines right now are the mRNA vaccines that cause our cells to recreate the spike protein that the COVID-19 causing virus uses to bind to our lung cells' receptors. I'm fairly confident from my limited understanding that spike proteins (or all types of envelope proteins, generally) are specific only to viruses, which don't help our bodies in any way. However, my concern is that I can't find any evidence or articles that specifically confirm that our immune system won't start targeting healthy ligands, such as hormones, other proteins, or even pharmaceutical drugs assuming they may have a similar enough structure to the mRNA-manufactured spike protein.

For example, this article suggests that the the SARS-CoV-2 S protein "allows an enzyme called furin, which is made by many types of human cells, to do the first cut...ACE2 is present in many organs throughout the body and interfering with it may have side effects, so researchers want to avoid hitting the receptor", suggest that it is possible that a vaccine response could have negative side effects to possible enzyme uptake. The article was written long before the vaccine was developed, so unfortunately it doesn't have commentary about whether or not the vaccine has been proven to accomplish that end.

Is there any research, evidence, or information that someone can link to that helps put my mind at ease on this possibility?

Since mRNA vaccines are novel and haven't had long-term test results, I'm frankly worried that there may be implications for such vaccines that may be more dangerous to healthy young adults more so than the risks of even the virus itself.

  • Remember that mRNA is very temporary. It's producing protein for a short time, just like the short-term exposure you have to any new pathogen whether it makes you ill or not, the contents of other traditional vaccines, etc. This isn't something new for mRNA vaccines.
    – Bryan Krause
    Jan 6, 2021 at 18:19
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    The mRNA vaccines being distributed now in some countries were tested in thousands of patients. If what you suggest would happen, you would see it in those patients. The memory cells don't need to wait to see their antigen again if the antigen is already present in the healthy person. It would also happen regularly with everything else that the immune system sees from the environment. There's nothing so special about this one antigen except that it's from a virus we'd like immunity to.
    – Bryan Krause
    Jan 6, 2021 at 18:34
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    What I am trying to get at is: why do you think this way of presenting an antigen is substantially different than previous ways or of natural exposure to antigens? Knowing this will help produce a directed answer and I think would count towards this site's requirement for prior research. Otherwise, questions without prior research are likely to be removed.
    – Bryan Krause
    Jan 6, 2021 at 18:47
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    That's just it though, (1) we know that mRNA vaccines are different than previous ways or natural exposure. They're novel, and therefore there is no research on long term effects. Previous vaccines have either been through viral vectors or through subunits of the virus' proteins. (2) My personal research resulted in a lack of answers, hence why I came here. There doesn't appear to be a discussion on the matter, hence why it's relevant to start one. Jan 6, 2021 at 21:00
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    @RyanSaunders Much better, thank you. Links aren't strictly required, but they are the gold standard.
    – Carey Gregory
    Jan 7, 2021 at 15:39

1 Answer 1


You say:

I can't find any evidence or articles that specifically confirm that our immune system won't start targeting healthy ligands, such as hormones, other proteins, or even pharmaceutical drugs assuming they may have a similar enough structure to the mRNA-manufactured spike protein.

"mRNA-manufactured" is a red herring here. If the spike protein could cause such an auto-immune response you'd see it from any vaccine that uses the SARS-CoV-2 spike in any shape or form (e.g the classic protein-subunit vaccines that are in phase III trials), as well as from the SARS-CoV-2 virus itself.

Now it's true that the virus itself does cause an immune overreaction in some people but this actually leads to ARDS often leading to death--something that would be hard to miss in clinical trials of the vaccine.

Speaking of such auto-immune reactions, some have been observed from the vaccines, involving cosmetic facial fillers. You can't compare these to ARDS.

It is a more reasonable question if "long Covid" reactions could be caused by administration of the vaccine alone, but again "long Covid" symptoms from the actual virus don't take months to emerge, even though various symptoms do persist that long. (I'm actually not sure how quickly the reactions observed in those with cosmetic facial fillers actually subside--maybe you can ask a more focused q on that.)

Furthermore, consider that phase II or III trials for the vaccines have been done for roughly 6-9 months now... (Actually, the FDA advisory on facial fillers is based on the two or so people who had them among the tens of thousands in the phase III trials. Those reactions were actually in line with the reactogenicity more generally observed in the trials--see another answer of mine here which touched on that. Note that that might not actually be from the spike protein though.)

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    Nice clear answer. Both of ours at medicalsciences.stackexchange.com/questions/25392 may also be relevant for people having "long term" concerns that aren't founded.
    – Bryan Krause
    Jan 7, 2021 at 2:42
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    Thanks Fizz! I think the information about (1) the spike protein also being present in previous SARS-CoV-2 vaccines, with no long term effects and (2) long term effects from Covid emerge very quickly, rather than a delayed effect really help ease my worry. That makes a lot of sense, thank you! Jan 7, 2021 at 6:51

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