Vero cells are used for many purposes, including:
screening for the toxin of Escherichia coli, first named "Vero toxin" after this cell line, and later called "Shiga-like toxin" due to its similarity to Shiga toxin isolated from Shigella dysenteriae.
as host cells for growing virus; for example, to measure replication in the presence or absence of a research pharmaceutical, the testing for the presence of rabies virus, or the growth of viral stocks for research purposes.
as host cells for eukaryotic parasites, specially of the Trypanosomatids.