We’ve all received the Covid-19 vaccine before, or at least know someone who has (hopefully), but we often see on our vaccination cards or on the news that the Covid-19 vaccine has this odd classification: mRNA vaccine. What is this mystery category of vaccine, how is it any different from other vaccines, and most importantly, how does it work?
Traditionally, vaccines have worked by injecting antigens into the body. These antigens imitate an infection and prime the immune system to respond to a specific threat in the future. The antigens that you are exposed to during a traditional vaccine are often dead, weakened, or parts of a specific pathogen. This exposure gives your body a “mini infection,” where your body has time to identify the pathogen and learn to synthesize specific antibodies against the pathogen. Antibodies are “destroyer proteins” that your body synthesizes during an infection; they bind to specific diseases and destroy them quickly. After vaccination, if you encounter the pathogen that you have been immunized against, you will not get sick because your immune system will already know how to produce specific antibodies to fend off that infection.
mRNA vaccines are different however; people first started experimenting with the idea of an mRNA vaccine in the 1960s. This makes mRNA vaccines a fairly new technology in comparison to their traditional vaccine counterparts, which were first developed in the late 1700s. In fact, the first mRNA vaccine to be approved for human use was the Pfizer and Moderna COVID-19 vaccines. So how do these new vaccines work?
First, let’s start off by describing what mRNA is, since it’s in the name of the vaccine after all. mRNA is a messenger molecule that aids in the production of proteins. Normally, when your body wants to make a protein, it follows this pathway: a section of a DNA molecule is transcribed (converted) into an mRNA molecule. This messenger molecule then leaves the nucleus of the cell (something that DNA can’t do) and travels across the cell until it meets a ribosome (part of the cell that makes proteins). The ribosome then reads the information on the mRNA and produces a protein accordingly.
The COVID-19 mRNA vaccine injects a small segment of COVID-19 mRNA into your body; this section of mRNA happens to be the instructions for how to create a COVID-19 spike protein. These spike proteins coat the surface of the COVID-19 virus and serve as markers (antigens) that our immune system recognizes when it deals with an infection. So when you are injected with the vaccine, your cells uptake the COVID mRNA, which then makes its way to a ribosome where it is read, causing your body to produce many spike proteins. As your body produces more and more of these spike proteins, the mRNA gets degraded until it cannot be read to produce any more proteins. At this point, however, your immune system begins to raise the alarm and attack the proteins that your body just produced. Remember, the spike proteins are a part of the COVID-19 virus; they are not harmful to you; however, they are still considered foreign bodies (they don't naturally belong in your cells), even if your own body produced them. As the immune response continues, your body learns how to synthesize COVID-19 antibodies, and you are effectively immunized against the virus.
In essence, the COVID-19 mRNA vaccine makes your own body produce small, harmless parts of the virus. This is groundbreaking because it exposes your body to a virus without ever having to inject or introduce your body to the actual dead or weakened version of the virus. This allows for mRNA vaccines to be developed much more quickly than their traditional counterparts, which may take years of trial and error to figure out just how much of the dead virus to inject or what strain of the virus to inject to ensure maximal immunization. All that you need to know when making an mRNA vaccine is information about the genetic code of the virus. You never actually have to worry about injecting the virus into someone, and thanks to new sequencing technology that allows us to read the genomes quickly, many mRNA vaccines can be developed in just weeks.
It is important to remember that the COVID-19 vaccine is the first instance where an mRNA vaccine was effectively used on a large scale. It is exciting to see where this newly proven technique will go in dealing with the diseases of the future. Regardless, it is important to note that mRNA vaccines are a feat of technological innovation. It took decades of research and development to get the idea of an mRNA vaccine into practice, or in this case, into your body.
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