evidence: Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use genetically engineered messenger RNA (mRNA). The mRNA in the vaccine tells your cells how to make a harmless piece of virus that causes COVID-19. After you get an mRNA COVID-19 vaccine, your muscle cells begin making the protein pieces and displaying them on cell surfaces. The immune system recognizes the protein and begins building an immune response and making antibodies. After delivering instructions, the mRNA is immediately broken down. It never enters the nucleus of your cells, where your DNA is kept. [...] - FDA approves and authorizes updated mRNA COVID-19 vaccines to better protect against currently circulating variants. U.S. Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-approves-and-authorizes-updated-mrna-covid-19-vaccines-better-protect-against-currently. Accessed Aug. 22, 2024.