The first COVID vaccine to be rolled out in the US, the vaccine from Pfizer and BioNTech, is an mRNA vaccine. The second will likely also be: Moderna’s vaccine is under consideration this week. We’ve never had a common mRNA vaccine before, so you’re not alone if you’re wondering what the hell this technology is and whether it has anything to do with DNA.
To answer the most common questions, no, it does not change your DNA. No, it’s not unproven technology (it actually is decades in the making). And the CDC has a fact sheet here with the basics you need to know about the new technology.
But here’s the very short version: The mRNA in the vaccine contains instructions for telling our body how to make a coronavirus spike protein. Once we do that, our immune system panics, as it should, and creates antibodies against the spike protein. The mRNA is destroyed shortly after the injection, but the antibodies linger. They can then recognize the real virus if we ever encounter it in the wild.
Would you like the longer, more detailed version? Here we go.
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Our cells contain DNA and continuously produce mRNA
Let’s start with a quick review of what it means to have genetic material. The DNA that we have as human beings is in (almost) every cell of our body. It contains instructions for everything a cell should do. Process food, grow more cells, release hormones – everything that happens in your body happens because your cells follow recipes encoded in your DNA.
Every time our cells use one of those recipes, the information in the DNA must first be copied. That copy, instead of another piece of DNA, is a slightly different type of molecule called RNA. (It’s a bit like DNA is a collection of reference books in a library. You can’t view the book because it has to stay in the library, but you can write down the information you want in a notebook with you. The notebook paper is RNA. )
Copying DNA to make RNA is a process called transcription, and the next step is often translation: Using the RNA instructions, now called mRNA, to make a protein. Proteins make up a large part of the structure of our body and small machines made of proteins perform almost all of our bodily functions. We are constantly making mRNAs and using these mRNAs to make proteins. Always.
The “m” in mRNA means “messenger,” and it refers to the type of RNA we are talking about here, the ones that transport information from DNA to the protein-making machine. (There are many other RNAs in the world, but let’s not deviate too much.)
The wild coronavirus contains RNA instructions to build itself
Before we talk about the vaccine, let’s take a look at how the virus that causes COVID, SARS-CoV-2, works in the wild. Viruses are smaller and simpler than all of our cells, and many scientists would argue that they don’t “live” the same way as humans or even bacteria.
A virus is made of proteins, sometimes encapsulated in a lipid (fat) envelope. The proteins themselves form the spiny spherical shape of the coronavirus. The red studs on that iconic illustration you saw are the spike proteins, but more on that later. There are 28 other proteins which make up the rest of the virus.
And in that spiky ball? There is a single long strand of RNA. This RNA is the genome of the virus and contains instructions to build all 29 proteins in the virus itself.
When the virus infects our cells, our own protein-making machine translates the viral RNA and makes the proteins it needs. We have been cheated; we just made a lot of virus components. Those parts form new viruses, each with their 29 proteins and a new copy of their RNA, and then they go out into the world to infect more cells.
(Again, I’m giving you a very streamlined summary of what’s happening; this article from Nature describes the life cycle of the coronavirus in all its nerdy details.)
mRNA vaccines instruct our cells to build the spike protein
A traditional vaccine would contain at least one protein from the virus or bacteria it targets, possibly a whole virus that has been inactivated or attenuated so that it cannot replicate. But an mRNA vaccine does things differently.
This vaccine gives us no protein at all, just a tiny lipid bubble (similar to the micelles in micellar water, the makeup cleanser) that envelops an RNA with instructions for making the spike protein. In fact, these instructions are formatted as a beautiful human-style mRNA, rather than the special tricky structure of viral RNA.
With these instructions, our cells can then make the spike protein (a bunch of those red nodules), but that’s it. The other 28 proteins are missing. So we don’t accidentally create viruses.
Our immune system can then respond to the spike protein
After making the spike protein, cells can place the spike proteins on their outside, where cells of the immune system can interact with them. Our immune system recognizes the spike proteins as foreign and not part of ourselves, and it sets up an immune response against them.
The immune response can include pain, fever, or fatigue. But you are not sick; your immune system just responds to the peak protein and prepares to recognize it in the future.
The mRNA from the vaccine disappears quickly
The vaccine mRNA does not linger. Just as our cells always make mRNAs, they also constantly destroy them. mRNA is a temporary messenger, used and disposed of within seconds of being created.
Although RNA and DNA are both nucleic acids, and are both ‘genetic material’ in a sense (DNA is our genetic material, RNA is the genetic material of the virus), the mRNA cannot become part of our DNA and does not change anything about us DNA. It’s a different type of molecule, in a different part of the cell.
Why mRNA Vaccines?
Different types of vaccines are being tested for COVID. Many use traditional technologies, such as modifying a cold virus so that it cannot replicate, and so it also contains a coronavirus spike protein.
But mRNA vaccines work particularly well in this situation because they can be made so quickly. If you want to make a lot of doses of a vaccine, you have to grow those viruses somehow. The flu vaccine is famous grown in chicken eggs, for example.
mRNA vaccines are faster because you don’t need any kind of cells to make them. The technology for mRNA vaccines has been in the works for many years, and 2020 just happened to be their time to shine. If you want to read more about how the vaccine was developed so quickly, we have an explanation about that here.