Covid Vaccine : How do they work ?
Updated: Dec 30, 2020
To understand this, first, there is a need to understand how viruses work.
Even though it isn't exactly clear how the Covid-19 virus works, most viruses have a very simple mechanism wherein once they enter the body, they penetrate the human cells and gives the cell instructions and information to replicate the virus. Most drugs against coronavirus are developed to counter this mechanism.
To further grasp this, we have to understand the structure of coronavirus.
There are mainly three proteins on the outer envelope of coronavirus, i.e. M, E and S proteins. While M and E proteins are primarily involved in the assembly of new viruses, the Spike(S) protein is involved in penetrating host cell and starting the infection in the host.
Notably, the spike proteins give the spike-like protrusions on the surface of coronavirus, which gives the virus the appearance of the outermost layer of the sun (the corona) hence the name.
The curious thing about viruses is they are non-living outside the host cell. Once they enter the host, viruses usually use its cells to replicate, hence there is a debate if they can even be considered to be living organisms. So unlike bacteria which is an independent entity with its own body to replicate, it's quite difficult to attack the virus without affecting the host cell. That's why there are so few antivirals and so many antibacterials.
Luckily, a crucial aspect in the fight against the viruses is the human immune system's ability to remember the virus if it had already infected the person before. This allows the body to trigger an early immune response when the body comes in contact with a similar virus in the future, hence not allowing the infection to spread.
So, in the case of coronavirus, it is believed that the spike protein triggers this immune response. So, what most covid vaccines do; is to introduce this spike protein into the body such that the body creates necessary antibodies; which will in the future, prevent the actual coronavirus from entering. However, the challenge is to introduce only the portion of the genetic code of the virus that contains the spike protein, so that there are no adverse reactions in the human body. Different vaccines have used different mechanisms for introducing the spike protein into the human body.
Some vaccines also introduce the weakened version of the virus so that , the body develops immunity to the virus.
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