No, the COVID-19 vaccine doesn't change your DNA. But it does make some long term changes. And that's a good thing.

Cartoon by: Maki Naro, from
gene.com/stories/the-antibody

One of the common tropes among anti-vaxxers lately is that the Covid-19 vaccine “changes your DNA.” Oh, the horrors!

Do they even know what they mean by that? Almost certainly not. Anti-vaxxers generally have no idea how biology works; often they are so confused that I’m tempted to say they are not even wrong. Even when they are right about something, it’s for the wrong reasons.

Many articles have already been posted explaining that the vaccine can’t alter your DNA, including a wildly popular piece at Forbes and explainers by the CDC and UNICEF.

So let’s dig into this strange notion that the vaccine changes your DNA. First, let’s look at what the CDC has to say:

“Will a COVID-19 vaccine alter my DNA? No. COVID-19 vaccines do not change or interact with your DNA in any way. Both mRNA and viral vector COVID-19 vaccines deliver instructions (genetic material) to our cells to start building protection against the virus that causes COVID-19. However, the material never enters the nucleus of the cell, which is where our DNA is kept.”

I see what they’re getting at here. They’re partly right, but in an attempt to give a simple “no” answer, the CDC got it wrong. It’s true that Covid-19 vaccines don’t directly alter your DNA, and it’s true that they don’t invade the cell nucleus, where your DNA resides. But that’s not the full story.

(The UNICEF article is more accurate and more nuanced, writing instead that “the information regarding harmful effects of the vaccine against COVID-19 on human DNA is unfounded and untrue.”)

Remember that the whole point of a vaccine is to prevent future infections. That means that something in your body has to change, right? So what is different?

Okay, take a deep breath and we’ll dive in. Whenever your body is invaded by a foreign cell–whether it’s a bacteria, a virus, a fungus, or some other pathogen–your immune system starts selecting from among millions of specialized proteins called antibodies, each one a little different. The way it does this is really rather extraordinary: many little pieces of your DNA are cut and pasted together, in millions of combinations, each making a different antibody. Eventually, one of these antibodies “recognizes” the pathogen (by binding to it).

What’s even more amazing is that the successful antibodies are “remembered” by the immune system, in the form of special cells called B-cells that have slightly different DNA! The DNA in these B-cells encodes just the right antibody to recognize the invader–the Covid-19 virus, that is. Once you recover from the infection, some of those immune cells (B-cells and T-cells–it's complicated) persist in your lymph nodes, constantly looking for any reappearance of the virus.

Or, as Ed Yong more colorfully explained:

“Picture the lymph nodes as bars full of grizzled T-cell mercenaries, each of which has just one type of target they’re prepared to fight. The messenger cell bursts in with a grainy photo, showing it to each mercenary in turn, asking: Is this your guy? When a match is found, the relevant merc arms up and clones itself into an entire battalion, which marches off to the airways.”

(For a deeper dive into how the immune system works, see Ed Yong’s feature article on this topic in The Atlantic from August 2020.)

The DNA in these special "memory B-cells is a little bit different from the DNA in all of your other cells. The vaccine itself doesn't stay around, but it "shows" the immune system a few copies of the spike protein from SARS-CoV-2, the Covid-19 virus, and the immune system remembers. And, I should note, a similar change to your DNA happens if you’re infected by the Covid-19 virus itself.

But B-cells are just a tiny, tiny portion of your body. Every other cell type, from skin to heart to lungs to brain, is completely unaffected by the vaccine. And if we didn’t have any way of “remembering” how to fight off infections, then we’d never become immune to anything, in which case the human race would quickly go extinct.

Finally, let me mention one other bit of misinformation. Early in the pandemic, some very well-known biologists at MIT published a paper claiming that the SARS-CoV-2 virus could, through an elaborate and highly implausible mechanism, integrate into the DNA of cells that were infected. This would indeed be worrisome! Many others quickly pointed out that this result could also be explained by more mundane mechanisms (experimental artifacts, essentially), and in the subsequent year and a half, with hundreds of millions of infections, no one has reported a single case where the virus actually did this. So not only is this event (reverse transcription of viral RNA into a human genome) really, really implausible, it also doesn’t even apply to vaccines, which only contain a small fragment of the viral mRNA.

(As an aside, that study by the MIT biologists was highly irresponsible. They were basically showing off their technical skills, saying “look what we can get the virus to do!” without considering how their work might be twisted, once anti-vaxxers got their hands on it. And the CDC response that I quoted above appears to be a direct response to misinterpretations of the MIT study.)

So back to our original question: does the Covid-19 vaccine change your DNA? Not directly, no. But yes, thanks to your own immune system, the overall mixture of DNA in your body is a tiny bit altered after you get any vaccine. Your DNA is also changed every time you recover from an infection, including the common cold. But the only change is in the DNA of a tiny number of immune cells, which hang around as guardians against future infections. And that’s a good thing.