The mRNA vaccines (Pfizer and Moderna) are kind of brilliant at a science level. I’ve had a few people in my real non-Twitter life ask me to explain how it works so I’m going to try my best here in this thread while I’m waiting for a patient to show.

The first thing to know is how your immune system works. Basically, your immune cells attack anything foreign to your body. If it sees a protein or a virus or a bacteria or anything that it doesn’t recognize, it launches an attack.

If it’s fighting off a virus, for example, it takes time to build up a full attack. It’s got to figure out what part of the virus to attack & ramp up production of what it needs to attack those parts. That can take a few days. Meanwhile the virus is replicating and expanding.

Once it fights off the virus, though, it remembers it. You’ve got memory cells in your immune system and if you run into that virus again, your memory cells say “I’ve seen this asshole before”. Your body uses it’s past experience to demolish the virus before it can make you sick.

So, with that in mind, we return to the vaccine. Scientists looked at the COVID virus and saw a protein on the outside of the virus that looked like a good candidate to launch an immune attack against.