MF59 is an oil-in-water emulsion of squalene, polyoxyethylene sorbitan monooleate (polysorbate 80, also called Tween 80) and sorbitan trioleate. Squalene is a natural organic compound originally obtained for commercial purposes primarily from shark liver oil, although plant sources are now used as well, including amaranth seed, rice bran, wheat germ, and olives. Yeast cells
