Why mRNA vaccines all of a sudden?
The typical vaccine injects you with a dead or attenuated (broken up) version of the pathogen you’re vaccinating against. Your body can then basically practice its immune response without dealing with the actual infection.
The immune system will be exposed to the relevant antigens (identifying molecules on the surface of the virus) and learn their shape.
It will develop memory cells and antibodies to prepare it for if you ever get infected with the live version. Simple enough… so why change it?
The mRNA vaccine causes your cells to build the antigens from scratch themselves rather than injecting them straight into the body.
mRNA is a short strand of genetic code your body can read to build a protein. In the case of the COVID-19 vaccine, the mRNA code instructs your body to build the infamous ‘spike protein’ we have heard so much about.
As you can see above, the sprike (S) protein is what allows the virus to latch onto our human cells.
Building these S proteins ourselves using the appropriate RNA code, allows our immune system to learn their shape, developing antibodies that can bind to them in the case of an infection.
Injecting people with mRNA instead of actual antigens has several benefits, mainly, mRNA is much quicker and easier to mass produce.
Secondly, using mRNA code is far removed from the live virus itself, i.e. it is not a virus that was once alive and deadly.
The mRNA only gives the body enough information to recreate the spike protein which is not a dangerous component but something like a latch the virus uses to stick to our cells.
These new vaccine therefore, may be thought of as safer and much less likely to cause an actual infection.
After your cell has made the S protein using the mRNA, it presents it on its surface. You immune system detects the foreign protein and develops an appropriate response without attacking or destroying the human cell. Your cell then destroys the S protein.
mRNA vaccines have been in the works for decades, their main benefit is that the process is much easier to standardise as it is simply producing a small piece of genetic code.
The great thing about this is that this code can quickly be edited in the lab and mass produced again should there need to be any changes due to a mutation in the virus.
The process can be massively scaled up, speeding up the manufacturing process in an emergency situation such as the pandemic we are currently facing.
Decades of research point to the safety of this vaccine, however there are some question marks about the efficiency.
Will these vaccines cause a strong enough response from our immune system to build strong immunity? I.e will our cells use this genetic material to produce a large enough dose of the protein to create strong immunity.
Also, has the correct protein been chosen for the vaccine? Should it be the S protein or should it be something else? Can fighting the one protein really prevent the entire infection.
All the arrows point to yes, it is the spike protein that the body must combat, and even if a traditional vaccine was administered, it is likely the S protein that the body would develop antibodies against.
The success and popular use of mRNA vaccines could potentially be a revolution in mass vaccination and shutting down epidemics with speed, precision and with less resources.
References
https://www.nature.com/articles/nrd.2017.243
https://horizon-magazine.eu/article/five-things-you-need-know-about-mrna-vaccines.html
https://apnews.com/article/fact-checking-afs:Content:9889529642
https://pubmed.ncbi.nlm.nih.gov/30972078/
https://pubmed.ncbi.nlm.nih.gov/28222903/
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html
https://www.health.harvard.edu/blog/why-are-mrna-vaccines-so-exciting-2020121021599
https://www.phgfoundation.org/briefing/rna-vaccines