Without these lipid shells, there would be no mRNA vaccines for Covid-19

Without lipid shells, there wouldn't be a bunch of other stuff. It's a way of delivering all kinds of other stuff into your cell, which also happens to include bits of mRNA.

I believe there are other covid vaccines that use LNPs to deliver spike proteins itself to make the cells present spike proteins on its surface so that it gets picked up by the immune system (kinda like the mRNA approach, but instead of making your ribosomes create the spike protein, you inject pre-made spike proteins)