COVID-19

mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. This immune response, which produces antibodies, is what helps protect us from getting sick from that germ in the future.

Researchers have been studying and working on mRNA vaccine technology for decades. Prior to COVID-19, they were investigated for prevention of various other viruses including Zika, rabies, and cytomegalovirus (CMV). mRNA technology has also been used in a variety of cancer therapies.

Protein subunit vaccines contain pieces (proteins) of the virus that causes COVID-19. The virus pieces are the spike protein. The Novavax COVID-19 vaccine contains another ingredient called an adjuvant. It helps the immune system respond to that spike protein. After learning how to respond to the spike protein, the immune system will be able to respond quickly to the actual virus spike protein and protect you against COVID-19.

Viral vector vaccines use a harmless, modified version of a different virus (a vector virus), and not the virus that causes COVID-19. The vector virus delivers important instructions to our cells on how to recognize and fight the virus that causes COVID-19.

Viral vector vaccines have been studied and used around the world for decades. Viral vectors were first developed for vaccine applications almost forty years ago when the vaccinia virus (VACV) was used as a vector to express the hepatitis B surface antigen HBsAg.

Since this promising first application of viral vectors for vaccine development, a variety of new viral vectors have been created using "prototypic" (model) viruses from many different virus families, including retrovirus, adenovirus, and poxvirus.

These viral vector prototypes have been used in a clinical trials against a variety of viral infections, such as Ebola, HIV, Malaria, MERS-CoV, RSV, Norovirus, and more.