Comparisons of mumps virus potency estimates obtained by 50% cell culture infective dose assay and plaque assay.

The two most commonly used methods for the determination of a virus potency are plaque assay and 50% cell culture infective dose (CCID(50)) assay, both based on cytopathic effect observation. We compared the potency estimates obtained by plaque and CCID(50) assays for nine mumps virus strains that produce different cytopathic effects in Vero cells. The ratios of CCID(50) and plaque assay quantification results differed for different strains and were in a range of 0.66-10, indicating that quantification results for some mumps virus strains are almost identical regardless of whether CCID(50) or plaque method is used, while the potency estimates of other strains strongly depend on the choice of the assay.