evidence: The Pfizer-BioNTech and Moderna vaccines use messenger RNA (mRNA) technology, which instructs the body’s cells to make proteins that trigger an immune response against COVID. The Novavax protein-based vaccine uses an older, more traditional technology and a different mechanism—it directly injects the spike protein (formulated in a laboratory) and another ingredient into the body, leading to the production of virus-fighting antibodies and T cells. The Novavax vaccine is the only non-mRNA COVID vaccine available in the U.S.