6.  Please describe "specific activity".

3. Lipid nanoparticles (LNPs) have emerged as promising vehicles for drug delivery. The latest successful use of LNPs is the recently approved COVID-19 vaccines by Pfizer/BioNTech and Moderna. One ofthe main components in the LNPs of these two vaccines is a synthetic ionizable cationic lipid. What is the central role of the ionizable cationic lipid in these two COVID-19 vaccines?