mRNA vaccines: what are they, and how do they work?

The first vaccine to make it across the line internationally and go into patients outside of a trial was the Pfizer vaccine. It’s what’s called an mRNA vaccine; we’ve never made a vaccine like this before. So how does it work? Martin Khechara explains...

Martin - Another way to show the immune system what an infection might look like is to introduce pieces of the genetic material from the infection directly. This is how the Pfizer and Moderna vaccines work. It’s brand new technology that has never been used to make a vaccine in humans before. Scientists there have taken a short piece of the coronavirus RNA genetic code containing the instructions for the spike protein that the virus uses to latch onto and invade our cells. Rather than put this into a disabled virus to get it into the body, they’ve instead wrapped up the pieces of code in tiny droplets of oil. When they’re injected, these stick to the surfaces of nearby cells and, just like two soap bubbles that stick and merge together, the oily droplets fuse with the cell surface and discharge their genetic cargo inside. The cells then read the genetic code and use it to produce large amounts of the coronavirus spike protein, provoking a protective immune response. The genetic material is eventually degraded in the cells, bringing the process to an end. Because these vaccines tend to be less robust than viral vectors, and they can be harder to make, they tend to be more costly and can also be more difficult to store and transport, which can limit their use.