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I'm seeing a lot of people wondering why this vaccine doesn't work against variants, but the mRNA virus shows little to no reduced effectiveness. I thought I'd spend a few minutes explaining why in (mostly) non-scientific terms. https://twitter.com/washingtonpost/status/1358529532878327808
The key difference between the two is in what they are: The Moderna/Pfizer vaccines are mRNA type, which means they carry the mRNA of the viral spike protein, whereas the others are weakened versions of the virus.
To better understand the difference, let's say you were building a house, and you want your contractor to build a deck. You give the builder a napkin sketch and tell him to build it.
He's going to build a deck. They're uniquely designed but all built in the same fashion.
He's going to build a deck. They're uniquely designed but all built in the same fashion.
This is an mRNA vaccine. Your body is given a picture for a "deck" and told "it's bad". In this case , deck=spike protein. Your body doesn't care what's attached to that "deck". It's irrelevant. See the protein, kill whatever has it attached to it.
the anti-viral vector is like giving your contractor an architectural blueprint with everything dimensioned out, right down to the number of screws he'll need.
It's only a "deck" if it looks EXACTLY like your blueprint.
It's only a "deck" if it looks EXACTLY like your blueprint.
This is how viral vectors work, they look at the VIRUS, not the spike protein.
And if it doesn't look exactly like your blueprint, it starts to resemble your deck less and less. Eventually, it's not your deck at all. And you ignore it.
And if it doesn't look exactly like your blueprint, it starts to resemble your deck less and less. Eventually, it's not your deck at all. And you ignore it.
So this is what's happening with these variants: the part attached to the virus is mutating (RNA=rapid mutations due to a lack of WC Base pair correction) and looking less and less the original virus that the vaccine was made from.
I hear you asking, "STEM - what happens if the spike protein mutates?"
The spike protein is targeted to a very specific receptor in the body, the ACE2 receptor. But if this protein changes even a little, the virus no longer can bind. It becomes "nonpathogenic" and dies out.
The spike protein is targeted to a very specific receptor in the body, the ACE2 receptor. But if this protein changes even a little, the virus no longer can bind. It becomes "nonpathogenic" and dies out.
This is basic Darwin theory: viruses mutate all of the time, but only the ones that mutate in a manner that allow the virus to propagate survive and spread. That spike protein would have to not just change, but change enough that it finds a new target.
The odds of that happening are astronomically against, since it would have to happen in an organism that was non-pathogenic (so it's immune system didn't kill it) and then transmit to a human host.
The other issue with viral vector is what is referred to as binding affinity, which you can think of "how smoothly does my key fit into this lock?". If you think of a virus as a key, and a receptor as a lock, the more they fit, the harder they are to keep apart.
Vaccines like J&J and AZ are designed to fit BETTER than the virus, so that they occupy the receptor first. But these new variants have better binding affinity than the original (evolution), and as such - the vaccine is less effective.
So while the Pfizer and Moderna vaccines are harder to get ahold of, the likelihood of the virus mutating to a point where the vaccine is rendered ineffective is much smaller than when using a viral vector vaccine.
But unfortunately mRNA vaccines can't be sent overseas.
But unfortunately mRNA vaccines can't be sent overseas.
disclaimer: I am NOT a virologist. I'm a biochemist. I work on the "locks" that virologists use to test their "keys", to continue my analogy. There are great virologists on this site who's work is fare more detailed than mine such as @aetiology and @angie_rasmussen .
Also disclaimer: Due in part to Twitter brevity and in part in order to keep people from getting lost in the minutia, I fully acknowledge I crammed a full semester of virology and enzyme kinetics into the span of a few tweets. If there is any concept you want more details on, ask
