Why mRNA vaccines can’t change your genome: a lesson from Elmer Elevator

The mRNA coronavirus vaccines do not alter human DNA, writes NCSE Executive Director Ann Reid, debunking a common misconception. To explain why your DNA is safe, Reid turns to a toothbrush-wielding rhinoceros, a flying baby dragon, and a boy named Elmer Elevator.

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Recently, I received a suggestion from a member of NCSE that we debunk a widespread piece of disinformation circulating about the coronavirus vaccines that use mRNA to generate an immune response. The false claim is that these vaccines can alter human DNA. Sounds scary, right? But, you will not be surprised to learn, it’s totally false.

I could go through all the reasons that it is impossible for the mRNA vaccines to alter human DNA — and believe me, I will — but I think you know by now that I’d rather give students the opportunity to figure things out for themselves. Ideally, they will also leave class with some sticky little piece of information that not only debunks the current rumor, but also prepares them to cope with the next bit of misinformation that might come at them down the road.

The fundamental problem with the false claim about mRNA vaccines, as with many assertions of gene-altering threats, is that, barring purely physical insults like radiation, making changes in human DNA is not that easy. If it were easy, organisms as complicated as humans, with genomes made up of billions of base pairs and coding for tens of thousands of genes, would have had a hard time successfully reproducing for millions of years. (To say nothing of the canopy plant, with 150 billion base pairs.) Quality control and defense against genomic tampering are functions very much favored by evolution.

However, the reason such alarming claims aren’t rejected out of hand is that very few people are likely to hang on to the necessary level of biological inside-baseball knowledge. Maybe you teachers will easily follow along with my explanations of what it would take for a piece of RNA to successfully change the human genome, but your students’ eyes are likely to glaze over pretty quickly….DNA? RNA? Nucleus? Cytoplasm? Endonuclease? Reverse Transcriptase? Stop! Too. Much. Jargon. And that’s your current students — what about the people who have been out of school for decades? They are definitely not going to remember how all this stuff works.

Personally, I think it’s all rather beautiful and awe-inspiring to learn how our cells do all the things they do to keep us alive. Right now, all through your body, lots of cells are busily dividing, making a full-length copy of a genome that is three billion letters long in a ridiculously small space — like assembling an aircraft carrier in your hall closet. You don’t even have to think about it — your cells just take care of it, no problem. Thanks, cells! To my way of thinking, to be genuinely appreciative, the least we can do is learn about what they’re up to.

But I digress. However cool we think the molecular biology of the cell, most people will not retain much of what they ever learned about it. They may retain some vague sense that DNA something something RNA something something protein something something mutations. And when your grasp of the subject is that tenuous, a claim that mRNA vaccines can alter DNA may not seem that preposterous.

But if they’re not going to remember the details, here’s the sticky little piece of information that I want your students to never forget. The human genome is well-protected. If you want to change it, you’d better come with the right set of tools. To make this idea stick, how about doing the following exercise with your students? Tell them this:

Tomorrow I will be giving a very difficult test. You may bring up to eight objects to class (or your remote desk). You can bring textbooks, cheat sheets, energy bars, your genius aunt — whatever you want. If you bring the right objects, I guarantee that you will receive not only an A on this test, but an A for the entire year.

When your students appear the next day, post the following list on the board:

  • A hairbrush and a hair ribbon
  • A toothbrush and toothpaste
  • A lollipop
  • A magnifying glass
  • A rubber band
  • A canvas bag large enough to hide in

Tell the students that these are the objects that they needed to bring to class in order to ace the test.

I’m pretty sure none of your students will have assembled that particular collection, so you won’t have to give anyone an A for the whole year on the basis of this test. There may be some moaning and gnashing of teeth, but the instructions were clear — they had to bring the right things and none of them did.

So that may seem a little mean, but they will like the next part.

One of my children's favorite books was My Father’s Dragon (have your students read it — it’s very short). In this delightful book, a boy tells the story of his father, Elmer Elevator, who, when he was a boy, traveled to Wild Island to rescue a winged baby dragon. The dragon had been captured and forced into servitude flying ferocious animals back and forth across an inconveniently-situated wide muddy river. Elmer was aided in his preparations by a wise old alleycat who had visited Wild Island. Together, these are the things they decided Elmer should take on his journey:

The night before my father sailed he borrowed his father’s knapsack and he and the cat packed everything very carefully. He took chewing gum, two dozen pink lollipops, a package of rubber bands, black rubber boots, a compass, a tooth brush and a tube of tooth paste, six magnifying glasses, a very sharp jackknife, a comb and a hairbrush, seven hair ribbons of different colors, an empty grain bag with a label saying “Cranberry,” some clean clothes, and enough food to last my father while he was on the ship. He couldn’t live on mice, so he took twenty-five peanut butter and jelly sandwiches and six apples, because that’s all the apples he could find in the pantry.

Over the course of Elmer’s adventure, he uses each of these objects. For example, the toothbrush and toothpaste serve to distract a hostile rhinoceros that threatens to drown Elmer in the pool he weeps in because his horn (the book says “tusk,” but rhino horns aren’t teeth) has grown grey and ugly. Only the jackknife, which Elmer eventually uses to saw through the ropes holding the dragon, makes any sense in advance. But every object is used, and every one is essential; without each and every one of them, Elmer would never have reached and rescued the baby dragon.

All right, I can hear you saying: “What in the Sam Hill does this have to do with mRNA vaccines?”

Well, this. For an mRNA vaccine to alter your DNA, it would have to overcome a series of challenges, each of which requires specialized cellular components that would have to be in the right place at the right time. Just like Elmer Elevator, the mRNA can’t just show up in your cell and expect to get past all the wild animals between it and the baby dragon, as it were.

You can lead your students through all the steps that would be necessary for the mRNA to succeed in altering your DNA. The mRNA from the vaccine would have to find its way into the nucleus, make a DNA copy of itself, unwind a stretch of DNA, engineer cuts or breaks in that DNA, insert itself into the DNA, copy itself into double-stranded DNA, fix the little cuts where the new piece was inserted, and finally wind the DNA back up again into its compact storage form. Maybe, that doesn’t sound so bad. If cells can copy their whole genome, maybe they can do all that stuff too! But in fact, each of those steps poses a huge barrier to that foreign piece of mRNA.

  • There’s no mechanism for mRNA to go from the cytoplasm into the nucleus. mRNA leaves the nucleus but doesn’t come back — like that slogan for Black Flag’s Roach Motels™: “Roaches check in but they don’t check out,” except in this case, mRNAs check out but they can’t check back in.
  • Generally speaking, human cells don’t make the enzyme — reverse transcriptase — needed to convert RNA into DNA. There’s a very cool exception to that rule (one of your students might want to go learn about retrotransposons and report back to the class), but a random piece of mRNA is not likely to find any reverse transcriptase hanging around waiting to help it get into the genome.
  • The DNA in each cell is tightly wound around proteins called histones. That’s the only way it will fit! Unwound, the DNA in each human cell would be six feet long. (Check out this cool website to find out how far it would stretch if you unwound all the DNA from all the cells in your body — amazing!) All that carefully wound up DNA doesn’t just unwind at random (thank goodness) — unwinding is a carefully regulated process carried out by a multi-unit protein machine. A random piece of mRNA can’t trigger that process any more than I can cause a Tesla Model S to construct itself in my driveway.
  • Making breaks in DNA is also a carefully regulated process. There are human enzymes that cut DNA (they’re called endonucleases), which are important in DNA repair. But they don’t just go around cutting DNA willy-nilly (again, thank goodness), and nothing about a foreign mRNA would induce them to do so.

I could go on, but I think your students will get the picture — every single step in the process of inserting a foreign mRNA into our genome is essentially impossible, so there’s just no pathway by which all the necessary conditions could be met.

“But wait!” you might say, “those retrotransposons got into our DNA somehow, and how about these new techniques like CRISPR/Cas9 that allow scientists to modify DNA at will?”

Such good questions! An automatic A+ to anyone who asked them! It’s absolutely true that there are ways to modify human DNA. Retroviruses can insert themselves into the genome, and CRISPR/Cas9 technology allows extremely precise genomic modifications.

Furthermore, as detailed above, none of the steps outlined above are impossible. Human cells can make and repair breaks in their DNA, unwind it, transcribe a single gene into mRNA or copy the whole genome, and then wind it all back up.

But the bottom line, and what I hope your students will remember, is that all processes in a cell are carried out by tightly regulated protein complexes that don’t just play with any old stranger, whether it’s a vaccine, a genetically modified food, or a nutritional supplement, that wanders into the human body. Unless that stranger is as clever as Elmer Elevator and brings along all the things needed to navigate these obstacles (which retrotransposons and CRISPR/Cas9, in fact, do), the human genome is going to be just fine, thank you. So if your students ever come across a claim that something can change their genome, they should remember this lesson and ask themselves, “Does that vaccine (or food or nutritional supplement or ...) have all the tools it needs to pull that off?” If not, then they have no reason to worry.

Note: With summer approaching, it seems like a good time to add that there is a way in which human DNA can be — and routinely is — damaged: ultraviolet light, the main source of which is sunlight, and which is the main cause of skin cancer. So while you don't need to fret about mRNA vaccines damaging your DNA, you really do need to put on a healthy dollop of sunscreen before going outside, okay?

NCSE Executive Director Ann Reid
Short Bio

Ann Reid is the Executive Director of NCSE.