How mRNA Vaccines Work

This animation shows how COVID-19 mRNA vaccines deliver directions to make a protein that educates our immune system, so it will neutralize the virus in future encounters. The mRNA-containing lipid particles are taken up by specialized immune system cells.


How mRNA vaccines work

Coronavirus. Like many viruses, it uses a protein on its surface to attach to and enter our cells. Antibodies that fit onto this protein can block the virus from attaching. Coronavirus mRNA vaccines teach our immune system to make these antibodies. How do mRNA vaccines do that?

mRNA is a genetic material that instructs our cells to produce proteins. The mRNA in the vaccine is wrapped in a layer of fat particles that protect it and help it get taken up by specialized cells of the immune system called dendritic cells. Once inside these cells, the mRNA does not enter the cell's nucleus or interact with DNA, but remains in the cytoplasm with other mRNA molecules, waiting to create the enzymes our body needs.

When ribosomes read the vaccine mRNA, pieces of the viral surface protein are made. These pieces are then displayed on the surface of the dendritic cell. The dendritic cell travels to a nearby lymph node, where it presents the surface proteins to other cells of the immune system. Some of these cells, called helper T cells, train B cells how to make antibodies that will fit perfectly onto the surface protein of the virus. Other cells stimulated by the protein pieces, called cytotoxic T cells, can kill virus-infected cells.  

Now, when the coronavirus tries to infect us, our immune system is ready. Immediately recognizing, neutralizing and destroying it before we ever even have a chance to become sick.