Notes: YK-009 is an ionizable cationic lipid (pKa = 6.512) that has been used in combination with other lipids in the formation of lipid nanoparticles (LNPs).{72006} Administration of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant mRNA in YK-009-containing LNPs induces the production of IgG that binds to the SARS-CoV-2 receptor-binding domain (RBD) in mice, with a boost in IgG titers 10 days after a second dose.