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.

That protein, by the way, is an important one for the virus. It uses that protein to get into your cells. That protein makes the virus more infectious. In short, that protein makes the virus more of an asshole.

Now COVID has DNA in it that codes for all of its parts. So scientists looked at the entire DNA sequence of virus and found the sequence of DNA that is the blueprints for that protein. The asshole protein.

Side note: DNA is the blueprint to make things in a cell. Cells take the DNA and transcribe it into RNA. The RNA is the instructions that tell the cell what to make. mRNA (literally messenger-RNA) literally just gives instructions to the cell to make something.

So scientists took the blueprint for the asshole protein on COVID and made an mRNA version of it. Literally just the instructions on how to make that protein. These instructions “are” the vaccine. Let me explain.

The vaccine contains no actual part of the virus. It has only the instructions on how to make the asshole protein. So, you can’t get infected with COVID from the vaccine. You just get these instructions.

Your cells see these instructions and say “sure, I’ll make this”. So your cells make a bunch of the asshole protein. You immune system sees this new protein you’re producing and immediately says “what... the fuck... is this?” And it starts attacking the protein.

Remember it hasn’t seen this protein before. It takes awhile to ramp up production. Then it launches an all out war against the asshole protein. The fevers, chills, muscle soreness, etc you might get as vaccine side effects is your body bombing the hell out of the asshole protein

So you destroy the asshole protein (which in and of itself can’t infect you, it’s just a protein, not the virus). Now here’s the important part. Your memory cells ‘remember’ the asshole protein. They remember exactly how to destroy it.

By the way, your body breaks down the mRNA instructions that you got with the vaccine pretty quickly too. That’s normal. You don’t need a bunch of instructions hanging around forever. Your body breaks those down and gets rid of them.

So you’ve broken down the mRNA instructions. You’ve destroyed asshole proteins. Everything from the vaccine is gone. Except for those memory cells who remember that protein very well.

So then, a COVID virus enters your body. Your body has never seen the virus before. BUT it’s seen that protein that’s on the outside of the virus. Your memory cells say “you’ve got to be kidding me, THIS asshole again? Get the fuck out of here!”

Your body’s own ‘natural immune system’ quickly and efficiently launches an all out war, using the template it has from when it destroyed the asshole protein last time. It destroys the virus before it can take hold, replicate, and make you sick.

Congratulations! Now, you’re immune to COVID! You’ve got the blueprints to defeat it as soon as it enters your body.

What if the virus mutates so it doesn’t produce the asshole protein any more? Well, since it uses the asshole protein to get into your cells, if it mutates away from the asshole protein, it’ll probably also be less infectious. That’s what makes the vaccine low-key brilliant.

This is correct. Sorry, I got caught up wanting to explain our own DNA-RNA process and went on autopilot. COVID is an RNA genome meaning it just uses the RNA directly instead of transcribing from DNA. The rest is the same.

We don’t know for sure. We have a very long memory for some viruses and shorter for others. We’ll have to see for this one. Sometimes we make up for a shorter memory with a “booster” vaccine some ways down the road. Like a little reminder.

Probably not. Most of the viral load comes from replicating in your body, not exposure. But remember the vaccine is 95% effective, not 100%. A lot of that depends on how robust your own immune response is to the protein and how effective your memory cells are towards it.

Reinfection from a virus you’ve had before could be because the virus mutated (in which case it’s technically a different virus) or because your ‘memory’ or that virus wasn’t as strong as you’d like.

I saw this awhile back and it’s, of course, brilliant. I wanted to break it down to step more basic than this and throw in a few more swears but Rob’s video here is fantastic.

Not by any way I can see. Your immune system, in all this, is working exactly the way it’s supposed to work. It attacks the foreign object and then remembers it for later. Your immune system at no point is altered. It’s out there doing it’s thing.

Hey everyone, there’s a lot of great questions that people have attached to this thread and I’m trying my best to answer them, but there’s a lot. Also, some are beyond my knowledge. You immunology / ID nerds out there, feel free to jump in in the replies.

There’s lots of questions about allergies in the thread. Here’s the best thread I’ve seen on it so far. tldr; don’t be TOO worried about allergies.

@WheatNOil Great thread and thank you for sharing. One question I didn't uncover in my own research yet: Why does it take two shots to essentially train our immune system? And why does it seem like it's the second shot that gives people the side effects when it does?

@brett_milam There’s some evidence that you get immunity (at least partial) after the first shot. But they wanted to make sure your body gets a good immune response & so we do it again. It’s like a second round of target practice so you’re ready for the real thing.

Friends I’m very happy people found this useful. Two things 1) If you have specific questions about whether the vaccine is okay for ‘you’ b/c your other conditions, (often autoimmune) please talk about it with your doc. That’s better than info from random me who doesn’t know you.

2) There’s SO many excellent questions and I can’t answer them all even if I ‘didn’t’ have a job and my own kids to be a father to. So I’ll do my best, but thank you to all the wonderful science nerds going through and answering for me. I see you, I appreciate it! 👊🏽

Ok, some more things. People wondering my credentials. I’m a physician, but not an immunologist. I’m actually a psychiatrist, but my job at the U of Saskatchewan is in medical education. So I try to explain complex stuff in simpler ways. (And I don’t ‘usually’ swear so much!)

Also, remember, we get a vaccine to protect ourselves, but more importantly to protect others around us, especially those who ‘can’t’ get the vaccine (or 5% who aren’t immune). We do this for each other, we get through it together. Get through the winter friends. Spring is ahead.

The 2nd dose is the same as the 1st and is there to make sure you get a good enough immune response for longer memory. ‘Maybe’ 1 dose would be enough but we don’t know yet. They did the trials w/ 2 doses to make sure it works. Extra target practice for your body!

We don’t 100% know yet. If you’re immune, you’re killing the virus quickly so it doesn’t have much time to replicate & spread. The Moderna trials showed less spread in vaccinated ppl who got the virus but had no symptoms. But less spread doesn’t mean no spread. 1/2

We’ll know more soon, but it’s safe to say once you get both doses: 95% chance you’re immune, you ‘probably’ spread less, but should still mask & try to distance so YOU’RE not the asshole spreading the virus to people who haven’t got the vaccine yet. At least till cases drop. 2/2

Here’s a thread on a common theme of questions I’m getting in the replies: What if I already got COVID and then get the vaccine? Related to that is how long immunity lasts.

Some have asked about the differences between Moderna and Pfizer. This article has it and is just a great summary of effectiveness and side effects.

On mutations and the strain circulating in the U.K. right now. Or, as I decided to call it (for no good reason) the sweater-vest asshole.

Dr Saxinger taught me half of all I know about infectious diseases and immunology (Dr Forgie taught me the rest) and her thread here summarizes CDC recommendations for immunocompromised, Guillian Barre, pregnancy, & allergies! (All Qs I’ve been asked a lot but couldn’t answer.)

(I realize now, too late, that tagging Dr Saxinger to my thread means she might read it and I’ll die of embarrassment if she sees my RNA / DNA mistake. Luckily, I remain partially anonymous. Sorry Dr Saxinger!)

On the AstraZenica / Oxford vaccine and how it’s similar / different than the mRNA ones.

On the Sinovac vaccine. (Also, h/t to @HockeywthHannah for describing Philip Broberg playing so injured as Weekend at Bernie-ing it, which led me to the analogy for this thread.)

Preliminary data: Israel seeing a reduction in infections after just 'one' shot of Pfizer vaccine. Meaning we have some evidence that the vaccine reduces spread! Getting vaccinated helps protect others! We expected this but it's nice to have some evidence.…

To be clear on the Israel data: There is still 'some' spread after getting the first dose, it's just much less. So we still mask up to be sure until cases go way down. Might be even less after the 2nd dose, we'll wait for the evidence. Hold tight friends, we'll get through this.

I’m going to place this here since I expect it’ll come up...

Rate of anaphylaxis: Moderna - 2.1 per million doses (0.0002%) Pfizer - 6.2 per million doses (0.0006%) Remember most vaccination clinics will have you stick around for 30 min after your shot so if you ARE exceedingly unlucky, you can be treated promptly…

A thread on the Novavax vaccine.