Cell Ess has been used in the adaptation of Vero cells. There are several groups currently testing for viral infection. There are other options instead or going completely animal free. It is possible to go mostly animal free a combination of Cell Ess and 0.1% FBS and maintain most characteristics of the original culture. There are also other supplements like adding BSA that may be beneficial. For Vero cells as with other cells with optimization, Cell Ess has worked well.