There are many different kinds of vaccines being explored to combat COVID-19.

The first two vaccines that received Emergency Use Authorization (EUA), use a technology called messenger RNA (mRNA) to protect against infectious diseases. To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies, but not mRNA vaccines. Instead, they teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. That immune response, which produces antibodies, is what protects us from getting infected or seriously ill if the real virus enters our bodies.

COVID-19 mRNA vaccines give instructions to our cells to make a harmless piece of what is called the “spike protein.” The spike protein is found on the surface of the virus that causes COVID-19 disease.

COVID-19 mRNA vaccines are given in the upper arm muscle. The cells use these instructions to make the protein piece. After the protein piece is made, the cell breaks down the instructions and gets rid of them.

Next, the cell displays the protein piece on its surface, similar to how the COVID-19 virus would. Our immune systems recognize that the protein doesn’t belong there and begins building an immune response and making antibodies, like what happens in natural infection with COVID-19.

At the end of the process, our bodies have learned how to protect against future infection. The benefit of mRNA vaccines, like all vaccines, is that those vaccinated gain protection without ever having to risk the serious consequences of getting sick with COVID-19.

In an Adenovirus-based vaccine, like the authorized Johnson & Johnson vaccine, scientists take part of the SARS-CoV-2 virus’s code (its DNA) and adds it to a modified adenovirus (the virus that can cause the common cold). This teaches your immune systems to learn to recognize and fight the SARS-CoV-2 virus without causing you to be infected. The vaccine will not give you the COVID-19 virus or cause you to be infectious to others.

University of Michigan: The Top 5 COVID-19 Vaccine Candidates Explained
CDC: Understanding mRNA COVID-19 Vaccines
Children’s Hospital of Philadelphia: Questions and Answers about COVID-19 Vaccines
CDC: Different COVID-19 Vaccines
MDHHS: How mRNA vaccines work
MDHHS: How Adenovirus-based vaccines work