COVID-19 vaccines work by preparing the immune system to recognize and fight the virus that causes COVID-19 without having to get the illness itself. Most COVID-19 vaccines achieve this by teaching the body's cells to make a harmless piece of the virus called the spike protein, which triggers an immune response including the production of antibodies to protect against future infection.
How mRNA COVID-19 Vaccines Work
mRNA vaccines (such as Pfizer-BioNTech and Moderna) deliver messenger RNA (mRNA) instructions into muscle cells. These instructions teach the cells to produce the spike protein found on the surface of the virus. The cells then display this spike protein piece on their surface, which the immune system recognizes as foreign. In response, the immune system produces antibodies and activates immune cells to fight off potential infection. After the protein is made, the mRNA is broken down and removed from the body. This process does not affect the person’s DNA. The body’s immune system "learns" how to protect against future infections by recognizing this spike protein.
Protein Subunit Vaccines
Other types like protein subunit vaccines contain pieces of the spike protein itself and an adjuvant to boost the immune response. When injected, the immune system recognizes the spike protein pieces as foreign and builds an immune defense that prepares the body to fight the real virus if exposed later.
Immune Response
In all cases, vaccines prime the immune system to produce antibodies and activate other immune cells specific to the spike protein. This immune memory helps the body respond quickly and effectively if exposed to the virus, reducing the risk of illness or severe disease.
Thus, COVID-19 vaccines provide protection by safely exposing the immune system to a target from the virus, teaching it to defend against future infection without causing the disease itself.
