Currently, there are two types of COVID-19 vaccines in the United States: mRNA and protein subunit.
The mRNA vaccine: This type of vaccine contains material from the virus that causes COVID-19 and gives cells instructions for making a harmless protein unique to the virus. It uses genetically engineered mRNA, which allows the recipient to make the S protein found on the surface of the COVID-19 virus. Upon vaccination, the body's immune cells begin making pieces of the S protein, displaying them on cell surfaces. The body recognizes that the protein is foreign and produces T-lymphocytes and B-lymphocytes that remember how to fight the COVID-19 virus if the body later becomes infected with the virus. This process causes the body to create antibodies to fight the virus.
The protein subunit vaccine: This type of vaccine includes a part of the COVID-19 virus that stimulates the immune system (S protein) and an adjuvant. An adjuvant is an ingredient that enhances the body's immune response to an antigen. The vaccine does not contain the entire virus. After exposure to S protein, and with the help of an adjuvant, your body creates antibodies to recognize and fight the virus in the future.
The viral vector vaccine: A third type of COVID-19 vaccine, known as a viral vector vaccine, was used from 2021 to 2023; however, it is no longer used in the U.S. In this type of vaccine, genetically modified material from the COVID-19 virus is inserted into a different virus, which is used as a vector to deliver the instructions for making antigens to the COVID-19 virus. These vaccines typically use an adenovirus as the vector to deliver the genetic material from the COVID-19 virus, giving the body instructions to make copies of the S protein. Once the S proteins are displayed on cell surfaces, the immune system responds by creating antibodies and defensive lymphocytes to fight the virus if a person later becomes infected with the COVID-19 virus.
Currently, there are three COVID-19 vaccines approved by the FDA for EUA in the U.S.: (1) Pfizer-BioNTech, (2) Moderna, and (3) Novavax.
