Expression of viral vaccines and other therapeutic proteins in Vero cells is a cost-effective method for the production of commercial quantities of a drug substance. This kit was developed using the final product and in-process samples for four different products from four vaccine manufacturers. These products included whole virus vaccines as well as recombinant proteins. The broadly reactive, affinity-purified, polyclonal antibodies demonstrate a high degree of conserved HCP across all Vero cell lines tested. The robustness of this sensitive and specific ELISA method facilitates successful validation for almost any product expressed in Vero cells. This kit has an LOD of ~0.7 ng/ml.