evidence: Covid-19 vaccination has been a big topic and we were curious on the role of excipients in such formulations. Not surprisingly both Pfizer-BioNTech and Moderna (source FDA) have quite similar compositions: Active Ingredient, Lipids and a saline solution. Lipid (oil) "bubbles" are tiny bubbles of lipid (oil) surround and protect the mRNA so cells in your body can pick it up both vaccines have Cholesterol as part of the composition. The Saline (salt) solutions are also different. Pfizer-BioNTech uses a common type of saline called phosphate buffer solution, or PBS. Moderna uses a tris buffer which aims to make the pH level of the vaccine close to that of our bodies. (Kerry McGee, MD) Pfizer-BioNTech COVID-19 vaccine (Comirnaty®) ingredients (Source FDA) mRNA (nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2)