What you need to know about mRNA vaccines Lipids are organic compounds that are insoluble in water. Both vaccines use a blend of lipids to coat and protect pieces of mRNA, which enter the cells of an inoculated person and prompt them to produce proteins that teach the immune system to fight the virus.In theory, lipids should be easy to produce at large scale, because only a small amount is required for each dose, and most are small molecules that are not complex to synthesize, experts who developed the technology told Reuters.