Should we be afraid of COVID-19 vaccines?

Jhave received several questions on this topic over the past week. Now that vaccination is fast approaching, even due to start next week, all this is clearly taking a more concrete turn for everyone. I was even sent a text written by a retired Quebec doctor who wondered why we opted for “RNA vaccines” when there were older and better proven technologies. So let’s see.

“Classic” vaccines consist of presenting so-called “attenuated” (made less virulent) or downright “dead” viruses, or even bits of virus to the immune system. This then learns to make antibodies, proteins that bind to the microbes of the vaccine to deactivate them. But the three vaccines that have completed clinical trials so far take a different “path” which, admittedly, is new and has not been tested as much as the “classic” vaccines.

The vaccine developed by pharmaceutical AstraZeneca and Oxford University uses a harmless virus (an adenovirus found in chimpanzees) to deliver part of the DNA of COVID-19, specifically a gene, into our cells virus that contains the “recipe” for a “spike protein” – a kind of spike on the surface of the virus that is used as a key to enter and replicate in our cells. Once the gene is in a cell, it will start to produce the viral protein, and this is what will trigger the immune system’s response. In short, instead of producing viruses (or pieces of) and injecting them, we make our cells do the work.

The other two vaccines, those from the companies Pfizer / BioNTech (which Health Canada approved this week) and Moderna, consist of injecting “messenger RNA” (mRNA), which is a kind of genetic material different from DNA but that everyone has too. And the principle remains essentially the same: this mRNA contains the “recipe” for the spicule, and it is our own cells that make the viral protein.

This is also the advantage of these “vaccine platforms”, as they are called: it avoids having to “cultivate” viruses, a process that is tedious and expensive, which allows vaccines to be produced much more quickly. .

Now, it’s true that the Wikipedia page on RNA vaccines says that when RNA gets directly into the blood, it causes it to clot – and it’s not just Wiki saying that, it’s the results. of a study. But it would be wrong to deduce from this that pharmaceuticals have found the solution to this problem in just a few months: the study cited by Wiki does not date from this year, but from 2007. And over the past 13 years, there were many, a lot research on mRNA vaccines.

On coagulation itself, the 2007 study mentioned that it was “naked” strands of RNA that caused clots. However, it is precisely not “naked” mRNA that is injected into these two vaccines, because that simply would not work. As we can read in a review of the scientific literature published in 2018 in the scholarly journal Nature Reviews – Drug Discoveries, RNA degrades very quickly when it is found on its own in the blood, so much so that in the first prototypes of RNA vaccines, mRNA did not have time to reach our cells, which could not therefore not express the viral protein. Much of the research in recent years has been to find some sort of “capsule” or transporter that allows mRNA to reach its destination. So the results of the 2007 coagulation study do not really apply to the vaccines developed this year.

Another problem that has arisen along the way is that RNA causes inflammation when it is in the blood, we read in another review of the literature published in 2019 in the medical journal. Vaccines. But then again, solutions were found and this article indicated that the results of animal testing and some human testing were “encouraging”.

That being said, these are still very new technologies: until this fall, no mRNA vaccine had ever been tested on large groups of people, let alone almost entire populations. The two literary reviews I am quoting here also warned that we should keep a close eye on a certain number of points, in particular this history of coagulation. But their authors did not have data from the three major clinical trials on COVID vaccines. These, it must be said, are very reassuring about “side effects”.

Almost 10,000 people received the AstraZeneca / Oxford vaccine, 15,000 received the Moderna vaccine, and Pfizer / BioNTech administered its vaccine to nearly 22,000 people. And the “side effects” seen on all of these people are very much in line with those of the “old” vaccines, that is, they are on the whole very mild and very predictable – for example: pain where you got stung, redness around the injection site, etc.

And that’s probably not very surprising, mind you. As we could read last September in the Journal of the American Medical Association, the way RNA or DNA vaccines work is not that different from some classic vaccines, basically, because when you inject someone with an attenuated virus, the virus enters their cells and replicates there. – which implies that our cells will produce viral proteins, a bit like with mRNA / DNA vaccines.

None of this, if it should be specified, constitutes a guarantee of absolute safety. It remains possible that extremely rare side effects, occurring for example 1 time in 100,000 or 1,000,000, will eventually be discovered when millions of people have been vaccinated. In addition, we do not yet have data on a long period (only two or three months for the majority of vaccinated): perhaps other side effects will appear later in some people. Perhaps…

We’ll see. But for now, all the data (and we are starting to have a large sample anyway) indicate that these vaccines are as safe as the others, that is to say extremely. It is not for nothing that the New England Journal of Medicine spoke last week, in an editorial, of a “triumph” of science …

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