Science Bits: How Does an mRNA Vaccine Work?

Since so many news outlets are abuzz about the new COVID-19 vaccines, I thought I’d take a few moments to talk about how they work.

First, to know how an mRNA vaccine works, we need to know a little bit about mRNA (and DNA).

DNA is a set of instructions, like blueprints, for your cells. Every single cell in your body has the same set of blueprints, but only some of them are used in each cell. The DNA lives in the cell’s nucleus.

DNA is copied into smaller bits that leave the nucleus so they can be used to make proteins. These copies are called mRNA. mRNA can be used as blueprints for every protein that your cells make. Proteins do practically everything. They make up your hair and eye color, they carry oxygen in your blood, they break down food for you, and they make up a lot of the structure of your body. They do a lot of other important things too.

Your body knows what its own proteins look like (usually). When your body sees proteins that shouldn’t be there, like ones found on the outside of viruses, your body knows it’s time to attack. Your body attacks viruses right away with a generalized attack, but also starts preparing a targeted attack that will go right after this specific virus very efficiently. The best part: your body remembers these attack plans, so next time it sees the same virus, it already has the targeted attack ready to go!

This is why you often don’t get the same virus twice. It’s also why vaccines work. If you can train the body to prepare the targeted attack without ever getting sick, like by showing your body a dead or weakened virus, you can fight off the real virus without ever having seen it first.

This is where the mRNA vaccine comes in. This vaccine, like the one currently being distributed for COVID-19, provides some mRNA for you. This mRNA tell your cells to make a protein, called a spike protein, that is found on the outside of the virus that causes COVID-19. Your cells make the spike protein and then destroy the mRNA. Your cells are not making the virus, or anything like the virus at all, except for that one little harmless protein that’s found on the outside of it. The mRNA never goes inside the nucleus of your cells and doesn’t go anywhere near your DNA.

Your body then recognizes this new protein as belonging to a virus and starts preparing its targeted attack. After two doses of the vaccine, your body has its targeted attack ready, which is able to beat the real virus more than 90% of the time. Meanwhile, you’ve never been sick or had to be exposed to the actual virus.

When preparing the targeted attack, your body might think there’s a real virus there (there isn’t) and try to attack it, which is why you might have some mild symptoms like a fever for a day or two, but this is not the same as having the virus and is not dangerous.

So what does that mean for us? If your doctor recommends you get the vaccine, get it when it becomes available to you. And yes, continue to wear your darn mask and stay home until enough people have gotten the vaccine.

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