An elevator pitch for mRNA vaccines.

• What are vaccines?

Our body has a self defense mechanism called the immune system which protects the integrity of our body from bacterial infection, viral infection, spreading of cancerous cells, destroying damaged cells etc.(Good brief of immune system) The immune system already has a huge database of things it knows it needs to correct for. So if a particular pathogen matches with one of the "undesirables" in the database the immune system responds to it using the "response" that is already encoded in. One key example is of your body temperature rising when you have a viral fever- it is a part of the bodies strategy to kill off the pathogen.

If the body does not know how to effectively respond to certain pathogens, the result is that the strategies taken up by the immune system does not amount to anything in stopping its spread in our body. It might not even be able to detect the viral particles early on (Tricking Immune Cells).

There's a part of the Immune system that learns on the fly, which is called the adaptive immune system. This part keeps a track of past infections and uses that learning to identify the pathogen early incase of a repeat infection. It is this capability of the Immune system that we are exploiting in making vaccines.

In the case of most horrendous diseases polio, measles, smallpox. rubella etc. The body takes a huge hit if we naively let it exposed to the pure viral pathogen. This could be fatal for a section of people. infected or leave them with long lasting side-effects. The vaccine mimics the pathogen in a non-fatal way so that the immune system learns about the viral pathogen. So if after this a real virus comes to attack the body, the immune system goes into action quickly and mounts a strong response stopping its spread.  

Some non-fatal mimicking of the vaccine are done using,

1. Structurally similar virus that is less fatal (Attenuated Or deactivated). This idea was famously used by Edward Jenner to make a vaccine for smallpox using cowpox which was similar but less fatal for humans. Further Examples : Yellow fever, measles, mumps,rubella. This has been the traditional method for making vaccines for a long time now.
2. Just introducing a subunit of the virus. This is used in a vaccine for hepatitis B which just introduces the surface protein.
3. mRNA: more on this in the next section :)

• What is mRNA?

We all start our life as a single cell (Fertilized human egg ~ 0.1 mm diameter) and it contains all the required information to make our entire body from that single cell (Pretty impressive right?). That's 750 MB to design your entire body. 

This information is encoded as a nucleic acid sequence [ A (adenosine) -T (Thymine) -G (Guanine)-C (Cytosine)]. The particular order in which ATGC occurs codes for different proteins, which is another another molecule that is used by the body to perform necessary task to maintain life.

These proteins are made outside the nucleus of the cell (structure of cell) in an organelle (specialized protein+ extra stuff) called Ribosome. To transfer the information from DNA which is inside the nucleus to these ribosomes on the outside, the cell uses mRNA. Which is sort of like an order request that the DNA sends to the ribosome to make a particular type of protein. 

Scientist have been able to synthesize these mRNA molecules in a lab, so that we can send it to the cytoplasm and make the ribosome do our bidding.

• How does mRNA vaccines work?

A mRNA vaccine for a disease is a synthetic mRNA that codes for a specific protein that is then delivered to the cell where is translated (jargon for making proteins from mRNA) using ribosomes. This protein then initiates an immune response, thus helping our body learn how to respond to the particular pathogen.

In the case of Moderna and Pfizers vaccine for COVID-19 it is the spike protein complex(The red things)  coded into the mRNA strand. (Beautiful video explaining Moderna's covid-19 vaccine). It is not the original spike protein found in the covid-19 virus but a modified protein that is stable just by itself.

mRNA are inherently unstable and are broken down by extra cellular RNses and does not make it to inside the cell. We therefore package it using a lipid(fat molecules) nano-particle envelope [aka A protective covering] in both the Pfizer and Moderna vaccines.

• Advantages over traditional vaccine development processes?

Traditional Vaccine paradigms have been attenuated/deactivated viral pathogens,Viral Vectors, injecting sub-units etc.

1. Rapid production capabilities: The first batch of vaccines from moderna was manufactured just 2 months after getting hands on the COVID-19 Sequence (Reference) . This was development speed that was necessary for the things to come, as the world shut down by March 2020 and millions losing their lives to this pandemic. Since everything is synthetic and you don't need huge bioreactors, cultures etc to scale production, mRNA tech became the silver bullet in this pandemic.
2.  Safety: Since this doesn't involve any viral pathogenic, there is no risk of infection or mutagenesis(The virus we injected doing stuff that we don't want it to do).

PS:I will be writing further articles on some of the conspiracy theories about vaccines and safety concerns. Didn't feel like writing it all in one go. 

Disclaimer: This is me trying my best to condense stuff down, and could have glossed over details.Please check out the links in the article for a more thorough understanding. This article is also susceptible to edits as I might edit it as I learn something more interesting.