How does an mRNA vaccine really work?
The Pfizer vaccine enters your body, does its thing, and is then destroyed. It does not alter your DNA, writes Katie Kenny.
The Covid-19 vaccines from Pfizer and Moderna marked a turning point, not only in the pandemic but also in vaccine development. They were the first approved use of messenger RNA, or mRNA, technology for human inoculation.
Often, vaccines are made using a weakened, inactivated or altered version of the virus or bacteria they’re trying to protect us against, to trigger an immune response. But mRNA vaccines don’t contain any pieces of the virus that causes Covid-19.
Instead, they use a chemical messenger to teach our immune system to recognise the virus as foreign. Importantly, and contrary to circulating misinformation, they’re not a form of gene therapy and they don’t alter our DNA.
DNA stands for deoxyribonucleic acid. RNA stands for ribonucleic acid. If DNA is the blueprint of life, then RNA are copies of those blueprints, explains Associate Professor James Ussher, at Otago University’s Department of Microbiology and Immunology. RNA converts the information stored in DNA into proteins, which are the molecules that actually get things done. So how does an mRNA vaccine work? The SARS-CoV-2 virus is studded with proteins that make it look like a spiky ball. These proteins help it enter human cells. Both the Pfizer and Moderna vaccines are based on the virus’s genetic instructions for building these spike proteins.
The vaccines use synthetic mRNA to deliver these instructions to our cells. But mRNA on its own is very fragile, so tiny delivery vehicles, known as lipid nanoparticles, are needed to transport and protect it. This is also why the vaccines need to be kept at very cold temperatures.
Once the mRNA reaches our cells, molecules in the cells read the instructions and build spike proteins. Our immune system recognises these proteins as foreign, and produces immune cells and antibodies in response. If we come into contact with the virus at a later date, our immune system will be able to recognise and attack it. Both Pfizer and Moderna vaccines require two shots for maximum protection. But we’re still not sure, exactly, how long protection lasts. What’s clear, though, is that these vaccines don’t alter our DNA in any way. The mRNA never enters the nucleus of cells, which is where our genetic material is kept. And, our cells destroy the mRNA soon after they have finished reading the instructions. Another phrase that’s being thrown around is ‘‘gene therapy’’, which involves altering the DNA of a cell usually to introduce another gene to correct a defect or give a new function to a cell, Ussher says. The vaccines can’t do that, either. Although this is the first time vaccines of this sort have gone to market, scientists have been working on them since the 1990s, he says.
And they’ve been studying RNA for ‘‘a lot longer than that’’.