Toriniwa, H., & Komiya, T. (2008). Long-term stability of Vero cell-derived inactivated Japanese encephalitis vaccine prepared using serum-free medium. Vaccine, 26(29-30), 3680-3689.
doi: 10.1016/j.vaccine.2008.04.076. 

In this study, a method of producing a Vero cell-derived Japanese encephalitis vaccine was established using serum-free medium, and tested its stability using various stabilizers during the inactivation process and storage at 4 degrees C and 28 degrees C. Similar to previously reported results of cell culture in serum-containing medium, Vero cells were cultured in a serum-free medium multiplied well, and the viral yield was successfully increased to about 10(9)PFU/ml. Following formalin-inactivation and purification via ethanol precipitation and sucrose density ultracentrifugation of the virus solution, the vaccine had the same quality as, and higher immunogenicity, the mouse brain-derived vaccine in current use. These results indicate that, in contrast to the current mouse brain-derived vaccine, the Vero cell-derived vaccine can be prepared using serum-free medium containing no animal-derived components.

The cells were cultured in VP-SFM, a commercially available product. The formulation of  VP-SFM is proprietary.