What’s in the COVID-19 Vaccines? We Asked Experts to Explain the Ingredients

Both the Pfizer and Moderna vaccines use messenger RNA (mRNA) technology. While these vaccines are the first of their kind, mRNA has been studied for more than 10 years, according to the Centers for Disease Control and Prevention (CDC). It was developed years ago to try to combat other illnesses, but never made it past early-stage clinical trials until it was refined and re-targeted for COVID-19. The vaccines use the piece of the encoded SARs-CoV-2 protein to trigger an immune response in your body. How? The mRNA gives your cells instructions to produce a protein that’s similar to the coronavirus’ spike protein, tricking your system into thinking it has an infection to fight. (Remember: It’s just a part of the protein, and does your body no harm.)